If he comes to BYU I think he will come with his eyes open that he will need to beat out Hall and Conover for the starting job. If he doesn't want to have that hurdle then Ole Miss and Lane Kiffin with a pass happy offense are waiting with open arms.
My bet is he goes elsewhere. BYU is a good program and Zach making it to the NFL helped, but there are so many metrics that say playing at OU and/or Ole Miss are better for a QB with NFL aspirations.