Have you ever seen powerful servers like Roddick, Federer or Sampras deliberately serving a straight 80 mph on their 1st serve? No? Me neither. Why? Because the returner would have ample time to position himself so that he could punish the **** out of it.
Unfortunately TS4 won't give you that option, returning a serve (non-kick or slice) so slow as if being puked out by a ball machine at full power. Cheesy players know that of course. ZPS is not even an option on 2nd serve because it's so easy to hit a good serve (100 mph+ even with Welch) all the time. Just waiting for a loophole that players will deliberately miss their 1st serve and then follow up with a ZPS 2nd serve and then claim that it would be realistic to do so.
In short, ZPS is unrealistic, cheesy and retarded.