Disclaimer: If I owned Avatar, Aang would have hair down to his butt crack, Sokka would be bald, and Zuko would wear a spiffy Dalmatian costume on the weekends just for Mai, to lessen the visual impact of his scar. Good thing I don't own Avatar, then.

Notes: This chapter focuses more on Zuko and a possible problem he might have. Honestly, I'm surprised that he survived Azula's lightning, as it would've been the perfect situation to kill him off in (also for Katara to kiss him). I suppose you COULD call this a sequel to "Fear the Melon Lord, Charlie Brown," but I don't, simply because I already said that wasn't a romance. So go ahead and ignore the fact that this was written after that, has mostly the same characters, ties up loose ends there, and would be a perfect sequel. Because it ISN'T. Yeah. Right... dangit.

Summary: Zuko didn't think when he leaped in front of Katara to block Azula's lightning. But that choice is one that will haunt him for the remainder of his life... however short that may turn out to be.

Heart Murmurs

An Avatar One-Shot

(I mean it this time, too!)

by Nate Grey (xman0123-at-aol-dot-com)

"You're certain of your findings?" Zuko asked quietly, his fingers digging hard into his knees.

The old woman nodded, her face grave. "Yes, my lord. I'm sorry."

His face hardened in response. "For what? You didn't do this to me. If anything, I did it to myself. It was my choice. I knew the risks."

"Do you wish for me to delay your guests?"

"No. Dinner will proceed as planned. And tell no one about this. That's an order." Zuko quickly threw on his shirt, trying to ignore the odd sensation of the old nurse's eyes on his back.

"My lord, certain arrangements must be in place," she finally added.

"I'll take care of them," he snapped, clearly irritated.

She flinched, but only slightly. "Do you require anything else of me, my lord?"

"Nothing." Zuko paused and sighed as he heard the old woman's footsteps move to the doorway. "But... thank you."

"Of course, my lord," was all she said before quietly closing the door behind her.

"Stupid," he whispered, staring at the small, dark scars on his fingertips. "So stupid..."

The dinners had been Katara's idea, of course. No matter how busy they all were with other duties, Katara had insisted that they all come together no less than three times a month and catch up with each other. It was a way of keeping them close and informed, and it gave Uncle an excuse to air out the old dining room and serve tea to everyone.

Katara was one of Zuko's more frequent visitors, sometimes for no clear reason. He suspected that she was all too aware that he'd saved her from Azula, and that she was unwilling to let either of them forget it. For a time, he'd appreciated the gesture, but now it was little more than a burden. He hated to look up, see her softly smiling face, and be reminded of what he'd gained, and at what cost.

But the dinners were in his own dining room, so he couldn't just decline to attend. Katara would be concerned and nosy, and Uncle would be hurt if Zuko didn't at least show up and drink a cup of tea with them.

This night, however, was even worse than usual. It would've been nice if that were only in Zuko's imagination, but he was nowhere near that lucky.

Katara and Aang were holding hands under the table again. Normally, this only annoyed Zuko slightly. Everyone in the room knew they were dating, but the two kept acting like it was the world's best kept secret, shooting each other sappy glances at any given moment and blushing. There were times when Zuko almost lost his temper and shouted at Aang to kiss her. They'd wasted so much time already, and there was no longer the excuse of a war to take things slowly.

As usual, though, Katara was leading the conversation, basically grilling everyone on how their lives had progressed since the last meeting. Zuko knew for a fact that she and Uncle gossiped with each other like there was no tomorrow, so it was no wonder that she knew the inner workings of the Fire Nation, sometimes even better than Zuko himself. He was already dreading his turn, because while his appointment with the nurse was top secret, Uncle had an uncanny way of flattering older, unattractive women and pumping them for info.

Sure enough, Katara's warm but piercing gaze finally landed on him. "You're awfully quiet today, Zuko," she commented. "Did the nurse give you some bad news?"

Everyone seemed to pause, waiting to hear his response.

Zuko made a show of rolling his eyes. "She didn't tell me anything that I didn't already know." Which was only half-true: he hadn't known the exact timeframe, only that he now had an irregular heartbeat, and a set of visible but easily-hidden scars on his fingers. Some people gave the gloves he constantly wore now a few odd looks, but never dared to question him on them.

The others seemed to relax, and Katara was distracted by Aang squeezing her hand, but Zuko noticed the way Uncle's eyes lingered on his face. "We'll talk about this later," was the clear message, and he gave the older man a slight nod to signal his acceptance.

That might have been the end of it, except for one thing.

Toph asked for a third helping of dessert.

Usually, Toph only ever asked for seconds. No one that had known her more than a day would ever be fooled into thinking that she was a proper lady, and she normally wouldn't have bothered trying to fool her friends. But it was her habit to eat no more than that while she was traveling, as Earthbending was so easy for her now that it only burnt off so many calories. If Toph ever ate thirds, it meant that she wasn't going anywhere for the night. That could only be bad news for Zuko, because while Toph was an excellent comrade in a fight, she was also even more stubborn than Zuko, a personality trait that made her hard to get along with, and even harder to avoid when she wanted something from someone.

Later, Zuko realized that it was his fault for forgetting that Toph was blind. It was a common mistake, even among her closest friends. Katara rarely led her around by the hand anymore (Katara preferred Aang's hand, and Toph preferred Momo, or someone willing to focus entirely on being her guide without distraction), and without such constant reminders, it was also easy to forget that Toph's rather unique skill set included being a human lie detector.

"So how long until you kick the bucket?"

Zuko frowned, looking up from the daily reports to find Toph sitting on his bed, turning a small statue of himself over in her hands absently. "You knew?"

"With your heartbeat, you might as well have screamed it at me. I always thought the story of how you bravely stepped in to save Katara was a bit too perfect. I mean, Azula may have always been crazy, but you don't normally survive a lethal attack from her with no scars to show for it. So I knew something had to be wrong with you even then. Now, how long?"

"Four and a half years, at the least. Five is being extremely optimistic."

She frowned, running her thumb over the statue's face. "You aren't going to tell anyone." It wasn't really a question, nor did Zuko expect it to be.

"I have to tell Mai. After all I've put her through, she'd never forgive me if I didn't."

"And that's it."

He shook his head. "I can't tell Katara. She'd blame herself. I can't take away her happiness with Aang. They've both worked too hard for it."

Toph grunted. "You picked a hell of a time to show your generous side."

"You think I should tell her?" Zuko asked in shock.

"No. I think you're giving up awfully easy. Have you even considered that another Waterbender might be able to help you? If nothing else, they might buy you some more time."

"What if it was meant to be this way? What if I don't deserve more time?"

"Nothing is meant to be, Zuko. There's what can be, and what is. Sure, it all worked out for Aang, but his people were wiped out, so the universe owed him big time. Plus he had the Avatar State to pull him through the worst parts. Everyone else has to make their own destiny. So if you're just going to give up, maybe you don't deserve Mai. Maybe you don't deserve to be Fire Lord. Maybe you don't even deserve to have an earthy goddess like me in your bed. But if you're going to turn into a quitter now, you sure as hell don't deserve to be my friend anymore. So go on and die, if that's what you want."

Zuko was startled to see a single tear slipping down Toph's cheek. He'd never seen her cry, and it bothered him, far worse than the thought of telling Mai, even more than the possibility of Katara finding out. Toph was one of his closest friends, one of the few he'd shared his darkest thoughts with, and he hadn't even considered how she would feel about losing him.

"Stop looking at me like that!" Toph snapped abruptly, wiping at her eyes. "If you're allowed to be stupid, then I'm allowed to cry a little!"

He said nothing, crossing the room and standing in front of her.

"What?" she demanded angrily, turning away from him.

Zuko slowly reached out and placed his hand on her shoulder. "I'd miss you, too."

She smacked his hand away. "No, you wouldn't. You'd be dead. Why else would I be so mad at you right now?"

"People die, Toph. And usually not in the way they'd prefer. Yue-"

"Oh, don't even bother bringing her up. She's just as dead as you'd be, and that's all there is to it! They can spout all the crap they want about the moon, but she's gone and she isn't coming back."

Zuko wasn't fooled. "You mean that I'd be gone and that I wouldn't be coming back. Right?" Honestly, after everything he'd seen from Aang, he wasn't convinced that Yue was gone for good. She had given up her physical body, but the moon itself was alive and well.

"You know exactly what I mean," Toph replied coldly. "I'm so mad right now I could kill you myself, except that I know it would turn Mai into an even bigger bi-"

"You're not helping," Zuko snapped.

"Good! Because if you ever got the impression that I was going to help you lay down and die, think again!" With that, Toph gripped the statue so hard that it crumbled in her deceptively powerful hands. Grunting, she tossed the pieces aside, stood up and stomped out of the room, very nearly bumping into the doorframe in her anger.

Mai returned to the palace later that evening, having been away on a diplomacy mission.

She only had to be around Zuko for a whole minute before realizing that something was very, very wrong.

"Are you going to tell me what's bothering you?" she asked as they walked through the palace gardens. "I'm only your girlfriend, and the woman you'll marry eventually."

To his credit, Zuko managed not to fall flat on his face. They had never even discussed engagement, much less marriage, but now he wondered how it could surprise him. Mai was always that abrupt, and she seemed to enjoy knocking him off balance. That made it far easier for her to win any argument they might be having at the time.

"Well?" Mai elbowed him lightly, which for her meant that if he hadn't seen it coming, he might very well have come away with a bruised or cracked rib.

"How do you feel about children?" Zuko finally asked, watching her face closely.

Something dark and ugly flashed through Mai's eyes before settling firmly on her face. "You want me to have kids before we're married?"

Zuko instantly backed away. "NO! I'm just asking!"

Her face instantly returned to the slightly bored expression that was so familiar on her. "Oh. They're okay in small doses, I suppose. It'd help if they could be born at age eight, though. You wouldn't believe how many diapers Tom-Tom went through in a day."

He could believe it, having been forced to hold Mai's baby brother once. Zuko had come away from the experience with a damp lap and a firm belief that Tom-Tom was either very sick, or very evil.

"So you don't want to have children," Zuko said quietly, unable to keep the disappointment out of his voice.

Mai rolled her eyes. "Don't be stupid. Of course I'll love OUR child. I thought you meant dirty, loud brats in general. Those I can do without."

Zuko froze, staring at her in wonder. "Then you do want children?"

"I want a child," Mai corrected. "I am not about to allow another sibling rivalry to tear the Fire Nation apart. You'll just have to be satisfied with whatever we have the first time, since it'll be the last time. Now, can we stop talking about kids, and start talking about you proposing to me properly?"

He winced. "But I had one more question about the child."

She glared at him, and then sighed. "What?"

"What if you had to raise it alone?"

Mai stared at him for several seconds. "I assume you mean because I would kill right now you for asking such a stupid question, yes?"

Zuko smiled nervously. "Not exactly."

"Okay, then why wouldn't you be there?"

"Suppose someone killed me?"

She blinked slowly. "Wouldn't happen."


"Would. Not. HAPPEN." She jabbed her finger into his chest for emphasis.


"Zuko, I love you, but you're really pushing it here."

He sighed, looking at the floor. "I need to know that you'd be prepared for the worst."

Frowning, Mai put her hand on his chin and made him look at her. "Why are you so convinced you're going to die, Zuko?"

"Because I am. Dying. Right now."

"Heh." Mai's lips twitched into a pained parody of a smile.

"Mai? Are you-"

Mai laughed again, then decked him. Hard.

When the stars faded, he looked up to see Mai standing over him, clearly restraining herself from hitting him again.

"You make me wait all of my life to be with you, and now you DARE to tell me you're dying? I could kill you myself!"

Zuko was really starting to wonder if every woman in his life was meant to threaten it.

Now Mai was pacing back and forth, muttering obscenities and throwing the occasional venomous glare at him. Had he been braver, or perhaps smarter, Zuko might have tried to run. Instead, he sat there, hoping Mai would calm down on her own.

Finally, she stopped, stared down at him, and sighed. "I must really love you. I'm actually considering forgiving you for this."

"If it makes you feel any better-" he began.

"Oh, shut up. It never does, when you start a sentence off that way." Mai shook her head, clenching and unclenching her fists. "Okay, you're going to tell me everything. And if you don't, I'm going to hit you again, only this time I won't stop until I've heard it all. And even then, I can't guarantee your safety."

Toph woke up in her guest room feeling particularly sick the next morning. She soon realized why: she'd cried most of the night, and hadn't gotten much sleep.

Also, Zuko was dying. That really sucked.

Zuko was her friend. She could readily admit that now, was even proud of it. There weren't many people that could get away with slapping the Fire Lord on the back, but she was one of them.

Beyond that, Zuko was a good friend, once he'd warmed up to the role (no pun intended). He wasn't shy about throwing his money around to show his friends a good time. He even continued to train with them, just to stay sharp, and didn't mind donning commoner robes again whenever they left the Fire Nation. Honestly, Toph liked the scruffy, wild-haired hunter Zuko better than the prim and proper Fire Lord Zuko. Fancy robes reminded her too much of the life she'd willingly left behind, and the one Zuko had been unwillingly cast out of.

Most of all, Toph liked Zuko's stance. He was rarely ever relaxed, always tensed and ready for his next move, like a big cat about to pounce on prey. It was probably an odd thing to like about a person, but Toph was blind, and she only had the vaguest idea what Zuko looked like. Of course, she'd heard about his scar countless times, and had even been allowed to touch it once or twice. But how Zuko looked didn't matter to her, any more than the fact that Toph was blind mattered to Zuko (she had cured him of any delusions he had about a helpless blind girl with a severe thrashing shortly after he'd joined their group).

But none of that was going to matter soon, because Zuko was going to die. Toph didn't care what he thought; it wasn't meant to be. No one that had fought as long and as hard as Zuko had deserved to die so young. It wasn't Zuko's fault that most of his family was born nuts. But it was so unlike him to just give up, though. He had so much to live for now, and the idea that he was willing to toss it all away was completely out of character.

Even worse, Toph couldn't talk to anyone about this. Normally, she kept her problems to herself, but this was really serious. She couldn't go to Katara, for obvious reasons. Aang was out because he could no longer keep any secrets from Katara. Sokka would blab, Suki would feel obligated to tell Sokka and Katara. For the first time, Toph realized just how inconvenient all of her close friends being couples truly was.

Toph was so distracted by her thoughts that she almost missed the door to her guest room being nudged open slightly. But there was no way she could miss the familiar weight and warmth landing lightly on her shoulder.

"Morning, Momo," she murmured, reaching up to scratch the lemur's chin. "Sorry, I don't have any food for you." She knew Momo hadn't come looking for food, though. With his nose, he could find the kitchen with no trouble at all. He was probably just looking for some attention.

Momo chittered contentedly and leaned into her fingers, curling his tail around her neck.

"Couldn't take Aang and Katara making out, huh? Trust me, I know the feeling."

"Oh, they make everyone sick," agreed a voice from the doorway.

Toph smirked, recognizing it at once. "Morning, Mai. So how's it feel waking up next to the Fire Lord?"

"I wouldn't know and don't start," Mai replied in a warm, but warning tone as she came further into the room. "I need you to be serious for a minute."

"Okay, no more jokes. What's up?"

There was a long pause, and then Mai asked a question that Zuko had asked her the previous day. "How do you feel about children?"

Despite her promise, Toph couldn't help the reply that flew from her mouth. "I'm flattered, but I think we're missing some of the necessary equipment to make that possible between us, Mai."

"We're not, actually," Mai said softly, before raising her voice slightly. "I mean it. Have you ever given any thought to having children of your own?"

"Once or twice," Toph admitted slowly. "Not like it's a dream of mine or anything, but I'm not completely against the idea. Why?"

Mai moved closer and sat beside Toph on the bed. "Because I need your help with Zuko."

"Ah. So he told you."

"Yes. And... wait. He told you?" Mai asked in surprise.

"Nope. I can tell when a man is lying."

"Is this one of those things only blind Earthbenders can do?"

"Something like that."

Mai shook her head. "You know, you're the only person other than Sokka that makes me wish I was blind. But in a good way."

Toph chuckled. "Thanks, I think."

Mai paused again. "Were you going to tell me if Zuko didn't?"

"It never came up. I knew he'd have to," Toph replied. "He loves you too much not to. Plus, you'd kill him if you found out any other way. Heck, I almost did."

Without warning, Mai reached over and grasped Toph's hands tightly in her own. "Listen, Toph. I need to share something with you."

Mai was not usually the touchy-feely type with anyone other than Zuko, so Toph knew this had to be important. "Okay, what?" the Earthbender asked calmly.


"Excuse me?"

Mai sighed heavily. "I know you love him, too."

"What? I don't-"

"You do," Mai insisted firmly. "I can tell. I can always tell when another woman wants him for herself. I don't mind so much in your case, because of what we've all been through. That, and I know he respects your strength and honesty. So do I. You may not even be aware of how you feel about him, but that's fine. Because I can tell that one day, you may love him even more than I do."

"You're crazy," Toph said at last. "Have you been drinking Uncle's tea?"

Mai laughed. "If you need any more proof, no one calls that man Uncle unless they want to be related to him."

Toph froze, suddenly feeling very guilty. "Mai, I never-"

"Don't worry about it. That's why I'm here. I want you to feel free to love Zuko. Maybe that will convince him to live, if I can't. You know, the Fire Lord is well within his rights to have two wives."

"Hold on! Who said anything about marriage?"

Mai's hands tightened on hers. "No one. But Zuko is NOT going to have a mistress, Toph. It's all or none here, got that? Anyone who tries to compete with me for his heart is going down, hard. But I wouldn't mind a trusted comrade helping me take care of him."

"Zuko wouldn't go for that," Toph insisted. "He loves you, not me."

"True. But he does like you. And sometimes, that's enough to start with. It was for me."

"No offense, but you don't really seem like the loveable type."

"I'm going to take that as a compliment," Mai answered. "And I have my ways, don't I, Momo?"

Toph was startled to feel Momo leaving her shoulder in hurry, chattering happily as he sprang onto Mai's arm. Momo was friendly, but he generally didn't get excited about anyone other than herself or Aang. "How...?"

"Amazing what a handful of fire flakes can do, isn't it?" Mai asked smugly. "I told you, I have my ways. But think about what I said, Toph. Please. I know you don't want Zuko to die, either. We need to give him all the reasons to live that we can come up with."

"You're dead meat, Fire Lord!"

Zuko winced at Sokka's choice of words, and at the loud slap of a chessboard hitting the table before him. "You haven't beaten me yet, you know."

"Yeah, but this time I've got a secret weapon!" Sokka said triumphantly. "Lady Luck herself!"

"If you mean Suki, her presence has never made a difference. You still lose."

"That's what you think!" Clearing his throat loudly, Sokka turned to the doorway. "Oh, lovely assistant! Could you join us, please?"

"For the last time," Suki snarled as she stomped into the room in full Kyoshi Warrior garb, grabbed Sokka's arm, and twisted it behind his back, "I am NOT your lovely assistant. I'm your woman, and you'd better get it right next time!"

"Yes, ma'am!" Sokka squeaked, trying to keep the tears out of his eyes.

"Good boy." Suki immediately released his arm and rubbed it tenderly, giving him a peck on the cheek. "Now go win your chess match. With your good arm, I mean."

"How is a bad arm going to help you?" Zuko asked as Sokka finally took his seat on the other side of the table.

"It isn't," Sokka snapped. "But Suki is! Everybody knows that Kyoshi Warriors draw their amazing luck from the spirit of Avatar Kyoshi!"

Suki and Zuko shared blank looks. "I've never heard that," they both replied at once.

"And you had better not be calling my years of combat training 'luck,' sweetie," Suki added in a warning tone.

"Of course not, sweetness!" Sokka said quickly, drawing Suki into a hug with his good arm. "I'm only saying that Avatar Kyoshi is smiling down on you, that's all!"

"Actually, from what I understand, she was very serious, and almost never smiled," Suki pointed out.

"Okay, well, then she approves of-"

"You win," Zuko interrupted, standing up quite suddenly.

"I do?" Sokka asked in surprise.

Zuko rolled his eyes. "Yes. I surrender. Forfeit. Whatever."

"Couldn't stand the waves of awesomeness rolling off of my good luck woman?" Sokka asked smugly.

"No, but if I have to sit here another second and listen to you two stall some more, I'm likely to pick up this chessboard and kill both of you with it."

The cocky smile dropped off of Sokka's face. "We weren't stalling!"

"Yes, we were," Suki corrected.

"We were?"

"Yes, that was the plan. You came to me and said, 'Stall while I dazzle him with my brilliant strategy, Suki!' I guess it was my fault for actually thinking that meant that you HAD a strategy."

"I'm still working on it, okay?!" Sokka shouted. "I can't always be the Great Idea Guy!"

"When were you ever?" Zuko muttered.

"Hey, I beat the last Fire Lord, buddy!"

Zuko blinked. "That was Aang."

"The twisted hunks of metal-"


"They never knew what hit-"


"Well, Azula didn't stand a-"

"That was ME!"

"Oh, right. Well, I TOOK OUT MELON LORD!"

Zuko stared at Sokka hard. "Are you honestly bragging about defeating a pumpkin?"

"See, you didn't-"

"And not even a rolling one! A stationary pumpkin!"

Sokka squinted up at him. "This is all because I hit you in the head when we first met, isn't it?"

"I'd forgotten that, actually," Zuko admitted. "But that must be what first convinced me that I really, really didn't like you."

"Yeah, I'd hate me, too, if I kicked my own butt."

"I don't even think YOU understood that," Suki chimed in.

"Not a word. But still! I did stuff, too!"

"Yes, you did," Suki agreed in an overly sympathetic tone, patting his arm. "My brave little man!"

"I'm not a little man!" Sokka protested loudly.

"Don't make me crack the whip, Sokka."

"I'll be good!" Sokka squealed, covering his head with his hands.

"That's just pathetic," Zuko snorted. "You're afraid of a figure of speech?"

"What figure of speech?!" Sokka bawled. "She owns an actual whip! I've felt it!"

"More than a few times," Suki added absently.

"I think I've heard enough," Zuko decided, moving for the door.

"I borrowed the whip from Mai," Suki said loudly.

Zuko stumbled, then hurried out of the room as Suki's laughter followed him. "Can't kill them, they're my friends," he reminded himself through gritted teeth.

"INCOMING!" shouted a voice down the hall.

Zuko spun around just in time to get a face full of mud. He angrily wiped his face and looked up to see Toph wearing a grin that stretched the length of her face, and Katara with a shocked expression.

"Toph!" Katara cried. "You said you needed that water!"

"I did," Toph replied. "Without it, that would've just been a dirtball, and it might've actually hurt more than just his pride."

With a roar of battle, Zuko launched a good-sized fireball at them, sending both girls scrambling out of its path.

"HEY! Aim at HER!" Katara shouted, already close to the point where she was considering supplying Toph with another mudball.

"He probably was, Sugar Queen," Toph snickered. "His aim just sucks is all."

Grinding his teeth, Zuko prepared an even larger fireball, a clear indication that he was not going to go out of his way to miss Katara.

Frowning, Katara looked at Toph. "Mudbending Wall?"

Toph nodded and giggled. "Oh, yeah!"

Zuko froze as Katara whipped out a small gourd and yanked the cork out of it. Water rushed out, forming a wall that stretched up to the high ceiling.

Toph stomped the ground, and a thick slab of dirt shot up just behind the water wall.

Knowing that he was doomed, Zuko extinguished the fireball and turned to run.

Katara commanded the water to saturate the slab of dirt, and Toph drove her fist into it, sending a volley of mudballs as big as her head flying after Zuko.

In that moment, Suki, drawn by the noise, stuck her head into the hallway. She took one brief look, immediately assumed that Zuko had done something incredibly mannish to piss off her fellow women, and tripped him as he passed by her. Then she ducked back into the room she'd emerged from.

"NOOOO!" Zuko yelled as he fell to the floor, only to be mercilessly pummeled by mudballs.

"GIRLS RULE!!" Toph and Katara shouted, just before bolting down the hallway and vanishing around the corner.

Zuko blinked and slowly rolled over, only to look up and see Sokka looking down at him.

"Dude! You just got knocked the MUCK out!" Sokka chortled, just before Suki elbowed him to shut him up.

"Whatever you did, don't do it again," Suki advised, tugging Sokka after her.

Zuko merely lay there for a few seconds before sitting up. He looked down at his ruined robes, sighed, and shook his head. He started to get up, then made of the mistake of glancing after Suki and Sokka. Sokka felt his gaze, glanced over his shoulder at Zuko and mouthed, "Dirty Water Tribe!" just before Suki elbowed him again.

"If I die, this'll never happen again," Zuko said quietly to himself. Then and there, he made a decision.

He was going to live... just so he could get those rotten girls and Sokka back.

The End.


I probably will add another chapter, eventually, to deal with Toph's feelings and if she ever does marry Zuko.

In my defense, I've watched Ice Cube's "Friday" and it's sequels WAY too many times.

Both Toph and Katara can bend mud, as seen in the show. Except I think the specific phrase for what they bent was "slurry," but mudbending sounds better. In other words, Zuko never stood a chance.

Katara is technically a Master Waterbender, but she lacks years of experience that a much older Master would have. So I'm assuming that she can't completely heal all mortal wounds yet, which is why I thought it a bit fishy that Zuko was perfectly fine after that lightning strike.