Pulev's defence is not that great. I think Zhang's express bombs find him in the first three rounds and blow him to bits.
Zhang blows him out of the water at this point. A decade ago this might have been a completely different fight but Pulev isn't the same fighter he was back then.
An up and down orthodox fighter with a very good left jab but only a decent right hand vs. a stone chin, huge, southpaw with a nuclear straight left hand and an atomic right hook? I don't see the scenario that leads me to believe Pulev survives more than a few rounds. You are not gonna just be a non moving target and beat Zhang............no way