Zuko's personality initially rubbed off Tidus the wrong way. He couldn't stand how demanding he was and thought he took things way too seriously. Now, he kind of admires that about Zuko, and he also can respect his loyalty to his friends, including the Avatar. He still thinks Zuko needs to have some fun, and plans to remedy that someday. XD But he can empathize with some of his experiences, and trusts him and would definitely be supportive of him now. He considers him a friend.