Why wouldn't he come to BYU? The fact that BYU gave Zach a chance is a pretty big deal and will go a long way with his family.
And it's not like BYU doesn't occasionally win recruiting battles with big time schools. Connover turned down Alabama to come to BYU.
And the fact that Zach is about to become the #2 pick in the draft is a pretty big selling point for any recruit.