#and Zuko is no longer relying on his anger and rage to fuel his firebending

[ofswordsandpens]

I fear that "fire bending didn't come easy to zuko" and "zuko isn't a prodigy" (both true) has somehow snowballed into "zuko is a bad or at best average fire bender".... which simply isn't true, especially by the end of book 3

[redrobin-detective]

I was on lunch break and I was watching the Firebending Masters and I had a revelation. I don't know if this was intended or not but it's what I believe.

It's been said from the very beginning that Azula was a better bender than Zuko, she was skilled and able to master the forms more easily than Zuko could. For me, I just kind of took it as differences in chi and ability between siblings. But in the beginning of the Firebending Masters, Zuko mentions he's lost a lot of his bending because he's no longer trying to capture Aang and has lost his angry drive. Later, after Zuko and Aang face the dragons, Zuko's firebending improves significantly to the point where he's easily able to take Azula in the final Agni Kai before she cheats and goes after Katara.

My point being, Zuko has always been a gentle and caring person at heart who was born into a family of ruthless murderers. He was taught from a young age to channel his rage and anger and superiority in order to conjure his fire but Zuko was never good with hate and thus it made his fire comparatively weaker because he didn't have as much "fuel". As he grew older and more bitter, he found it easier to use with all the tragedy in his life (maybe this was partially Ozai's intent in addition to getting rid of him?) but his bending clearly was weaker than Azula and Zhao's because he couldn't bring himself to hate with every part of being. He was angry throughout most of the series but there was no real hate. The Sun Warriors said that Iroh also learned from the dragons and learned a firebending style that was both powerful and not driven by hate which I do thing was a key turning point in his life and helped him become the Uncle we know and love. I bet Iroh instructed Zuko in the dragons' way during his exile but Zuko was too lost in his grief and shame to appreciate the nuances and still tried to pull his bending from rage (which led to... most of his outbursts in the series)

My point being, rage-fueled fire bending was unsuited to Zuko's personality and him trying to force himself to adapt is like trying to teach a dyslexic kid to read the normal way. It's not right or wrong, he just needed a different technique and once he found it and mastered it, I believe he was just as capable a bender as Azula was. There was no inherent difference in skill between them, Azula just found it easier to tap into her inner rage than Zuko. But we see with the finale that form of bending was unstable, it pulled all it's energy from hatred and anger and was a major factor in breaking Azula and led to Ozai's evil plans and arrogance to think he could defeat a basically fully realized Avatar. Meanwhile Zuko and Iroh were much more stable with their bending but also with their mental and emotional health. By not relying on anger all the time, they could sustain their bending longer and not suffer the consequences of other benders

TL;DR: Zuko's bending was weaker than his family's from the start because his personality wasn't suited for rage-fueled bending like Azula and Ozai. Only when he learned the dragons' way, fire-bending not controlled by rage, was he finally able to properly use his bending and become just as powerful as Azula only with more mental and emotional stability.