A commercial ZTR can cut in half the time i.e. 45 minutes depending on how many trees etc and how rough the terrain is.Can't say I agree with that. Depends on the deck.
I've owned zero turns, 3 point side and rear discharge mowers. My opinion the MMM I had on my old JD 850 ranked right up there with as good as if not better cut than any of them
A ZTR is rougher on the grass with more tear up on turns.