When you have 4 way battles like this I don't think its a simple as Jiaiya>Kisame>Nidaime>Zabuza. Zabuza probably isn't as badly matched up as it would seem. He's a stealth killer, say he gets his hidden mist jutsu off at the start, that immediately puts the 2 leaf ninja at a bit of a disadvantage seen as its probably the technique thats most annoying to go up against if you're not used to it. He's definately the weakest of the 4 if it was 1 on 1 battles, thats clear to everyone, but I think he is of a high enough level (I mean c'mon he fought Kakashi, the actual matchup was against him but put him against someone that is considered Kakashi level, Gai or Kabuto for example, and imo if they got trapped in the mist they'd be finished, lets not forget Kakashi had to be saved at first and he had the sharingan) to not be able to say "oh he's the weakest of the lot, he's dead straight away" in a 4 way battle. Now if you was to swap one of the other 3 with Neji or Hiashi then Zabuza's at a REAL disadvantage. I'm not for one minute saying he'd win this 4 way battle but saying Jiraiya wins because he beats Kisame who beats Nidaime who beats Zabuza just don't cut it. At least you could say what you think he'd do to actually come out the victor. He's not against genins here, he may be the strongest of the 4 if they were 1 on 1 battles but that doesnt necessarily mean he'd come out on top in a 4 way battle.