Hear's my theory:
The rescueing of Suki takes place in The Boiling Rock Part 1.
Zuko gets captured during Part 1. Somehow. I know this from a neat pic from SDCC that showed Zuko being lectured by Mai in a prison cell. Kindof her way of saying "Its not you, its me. But we can still be friends on EmoSpace."
Part 2, Zuko breaks out. Probably he is being held on one of those giant Zeppelins, which are heading to the WAT to kill/maim/disfigure/alloftheabove Aang and co.
Sokka is probably all liek "We have to go save him" and then Katara's all mean, but Suki tells her that Zuko isn't a bad guy.
And then we get the nifty picture above as Zuko jumps from the War Balloon and is saved, but poor Azula looks like she's falling to what mortals call "death."
But Azula lives. She lives.