Zuko stares for a moment, not really sure what to make of that. What IS he supposed to make of that? Suddenly he appears in the middle of a bunch of screaming machines, gets pulled into an alley by some weird metalbending freak, and is told that he's a younger version of himself? This is UNBELIEVABLE. And he does have trouble believing it. It's written all over his face.

"So you're saying I'm in the future? That's impossible!"

Really, this guy has to be pulling his leg right? But he has this feeling that he's not. He doesn't look like the kind of man that would joke. Lie maybe, but not fool around. He then pauses and picks up the mask with a frown, not really knowing if he should believe this guy or not. But he did just save him. No matter what his reasons might be, it's still true.

"Thanks, I guess."

But that still doesn't mean he trusts him.