Zabuza would probably use his Hidden Mist jutsu to kill Hidan effectively, and I simply don't see how Hidan is winning in that scenario. Hidan's reaction doesn't seem noteworthy and nearly everything about it seems to make it look lackluster. There were multiple times where Shikamaru managed to screw him over right in front of his own face due to his inability to respond to or even notice Shikamaru's actions. Though Shikamaru could simply be faster than the databooks say, I'd like to believe Zabuza is faster than him. Within the Hidden Mist, every action should simply be a reaction to the sounds you hear or attacks you receive, and Hidan doesn't seem to cut it.
Scenario two is given to Team 7. Zabazu only has two hands opposed to his opponents' 8. His most effective method to restrain anyone is his Water Prison and that requires him to become stationary and have one hand(and handseals along with it) become unusable. His clones are ass and got demolished by Team 7's genin, and their response to Hidden Mist is to bundle together, which makes restraining or knocking out any one Team 7 member that much harder.