[Things Bart is not actually expecting Zach to say: that he knows Zatanna. Which, all things considered, is kind of dumb. They're both magicians, so it'd make sense for them to know each other. Just like speedsters know all the other speedsters. It's just a Thing.

Bart is now going to comment on that Thing.]

Hey, you know Zatanna? [Totally brightening up at that because mutual friends! Ish.] Right, you guys are both magicians. So does that mean you guys are both in like some super secret magical society or something?

[He kinda missed the 'cuz' part.]