I am one of the few apparently on this board that thinks very highly of Zoo. Personally I think he's a very tough style matchup for Pac OR Mayweather and would win this one. Pac's workrate would give him problems but Pac's style is one of timing and in-out motion...but really...you aren't going to out-time Zoo, that's his bread and butter. If you aren't backing Zoo up, you're going to be kept on the outside and lit up with right hands (which, oh by the way, Pac is continuously a sucker for). Also note Pac is making his fame fighting bigger guys who simply don't have an answer for someone as fast as he is. Zoo made his living off beating guys faster than he is. Zoo by MD or UD.
I think Manny's speed, workrate, and movement would pose too many problems for him. He's a master of timing, but Manny is so unorthodox it would be very difficult to time him. I would give Zoo a shot, but I'd look for Manny to outwork him.