First, the most center minutes will go to Bam Adebayo, Miami's first round draft pick. Adebayo is a very talented one-and-done player from Kentucky who needs the preparation for the NBA. At 20 years old, he needs to play as much as possible.
Regarding Zach, I really don't think he is an NBA player. He is a better athlete than basketball player.
On offense, he was good playing screen-roll in college; but he has neither a center's post game nor a forward's outside shot. On defense, he was a good shot blocker helping from the weak side; but he never was a very good one-on-one post defender.
Zach needs to become a forward or a center. It doesn't matter which one he chooses; but when he does, he has to develop his game accordingly. If he wants to make an NBA team as a center, he needs to defend the post better and become a threat to score or pass when he gets the ball in the block. If he wants to make an NBA team as a forward, he needs to develop a reliable outside shot.
Or he can go to Europe, play in a league his current skill set will support, and make a nice living for 10 years.