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Ok so actually explaining their parallels/similarities
The main thing Zuko and Korra have in common is their character arcs. Now they're obviously not a one to one but when looking at then from a broader scope we can see that they both start the series as arrogant, hot headed, and ready to throw a punch but end the series as someone who can understand the struggles of the people around them and can be sympathetic to someone who they don't know and it takes them suffering to get there.
Korra says it herself at the end of season 4, "... but I finally understand why I had to go through all of that. I needed to understand what true suffering was so I could become more compassionate to others," both her and Zuko suffer and in doing so, learn sympathy. Zuko almost starves during his time in the Earth Kingdom and struggles with he whats to do with his life now that he's "settled down" in Ba Sing Se and then struggles with getting what he thought he wanted and realizing that after everything he's been through he's not the same person and doesn't want to be crown prince anymore. Korra has the avatar spirit ripped out of her and struggles with the fact that now Korra is all on her own with no past avatars to go to and then Korra is paralyzed from the waist down by the Red Lotus and struggles through relearning to walk while feeling useless and neglecting her avatar duties and friends while she dealt with the PTSD caused by the Red Lotus that haunted her for years.
Korra and Zuko also share the act of cutting their hair at the beginning of their journey to overcome their truma. For Zuko it's his father and his abuse and for Korra it's almost dying and being poisoned, and while they go through this journey they both have a solo episode of the same name (Zuko Alone & Korra Alone).
They're both also very ignorant to the majority of the world at the beginning of the series, with Zuko having traveled the world but not seen the world (the atrocities the Fire Nation committed) and Korra never having left the South Pole until she was 17 and therefore not understanding the people and the things happening around her.
I've never seen anyone talk about their parallels so either everyone knows and doesn't care or I'm insane. Zuko and Korra are some of my favorite characters so screamed when I saw that 'Korra Alone' title screen and I've seen them as parallel characters since then. Mako tried to do what Zuko did but without the character development and it did. not. work.
I think Korra is the true Zuko copy in tlok, and that's not to say Mako isn't he's trying to duplicate Zuko at his surface; a bad boy firebender but Korra, she duplicates Zuko at his core and in his character arc but y'all aren't ready for that conversation yet