Church! That is the reason Zab had success... for 3 and 1/2 rounds. He just out boxed him. Faster, trickier, and beat him to the punch. That was the single most "competitive" fight he has had at WW and that was damn near a shut out AND by a smallish WW. Since then many tried to overwhelm him and all have lost one sided decisions or got a gift in a card.
Yup, and that is why I don't see Floyd losing anytime soon. Because I don't think there are too many fighter out there with the raw talent Zab had for, as you said, about the first 3 1/2, 4 rounds.