I think Zab's only chance is to catch Floyd with one perfect knockout shot.
I'd probably have to recommend Zab go out stalking-aggressive against Floyd.
Not recklessly throwing looping arm shots, but more of a Mike Tyson-esque stalking aggression.
And hope he lands that one big money shot.
I believe that's his only chance.

If he wants to play it safe and box, I think Floyd will have a field day beating Zab to the punch every time.
Landing his best shot of late, his right hand lead, all night long on the southpaw.
If he wants to let Floyd be the aggressor, Zab can not fight backwards. Easy TKO for Floyd.

He needs to land that one big lucky shot on Floyd.
Stalking aggression.
Fighting backwards for any period of time = bad news for zab.