Take volume away from him and put him in better spots, he's a weapon. As a fourth or fifth option in a passing offense, he'd be nice to have.
I bet he ends up somewhere like LA or GB and does well.
The other knock on him is he's only played 1 full season since being drafted.
I guess if he comes on a cheap, prove-it deal....it'd be worth a flier. But my expectations would be super low. I think there's better options out there.
EDIT: thought about it some more...and it's a hard pass for me. Zach really needs a reliable pass catching TE to help take him to the next level in his development. I don't think Engram fits that bill.