There are two different sides of the ball.
Offense. I've noticed Z is put in pick n pop situations mostly. Very rarely do I see him operating as a traditional post big man on the offensive end. I think offensively, he provides spacing. Everyone sees the value in Z on the offensive end.
Defense. At 7' you have to at least be able to defend in the post. Most of the time, he will be matched up on traditional bigs that are playing that way. I see a player that has never done that. He gets muscled, can't hold his ground with fouling, and gets lost when put in a pick n roll. He is not even slightly prepared to defend traditional offenses. He cannot be in the game on the defensive end.
If we happen to play against teams without defensive big men, Z defense may not be as pick of a problem. But, clear as day, he was destroyed against Gonzaga. And Ole Miss bigs (Cisse and Sharp) would have been a problem. I think he is a situational player for us.
For the record, UGO should be #1 on the depth chart at the 5 imo...for his rim protection alone. He covers up our inability to stay in front of the other teams' guards.