As fighter they are both excellent, and both have extremely big mouths which funny enough i like. This would be a super fight. Zab isnt much bigger than PBF but punches harder, as for speed, i'll call it even, but i think PBF is a slighty better boxer.

If Zab brings he boxing brain, i'll tip him to win, But you never know with him, thats why my head says PBF by a narrow points decision.