Basically in Zone Coverage what you wanna do is drop to your landmark, which is the backend of your zone (For flats its outside the numbers, for hook to curl its the hashes). If you don't see anybody in your zone (in front of you) or approaching your zone, just drop further until you see a WR again.
The defensive camera is perfect for this because you wanna read the QB in Zone as well. (and have in mind that a defender in the NFL doesn't see whats behind him while dropping too, because his torso will face the QB most of the time.