Yes, against some extremely terrible defenses, Heaps did have some fun games. Against any defense that was better than a five mph breeze, his stats were terrible. His overall freshman stats were awful, even with those four games where the defenses were flat out atrocious.
Zach's freshman stats are actually pretty dang good, so right there the comparison between Zach and Heaps is null and void.
Mangum...good kid. But some things happened after his freshman season and he never recovered. After a pretty good freshman year, his confidence and his arm both regressed.
Zach had that shoulder injury so there's a comparison there to Mangum, but that's where it ends. Zach hasn't been dealing with anywhere near the other off field issues that Tanner did.
One last note, Zach's stats last year were comparable to a senior Max Hall. That's impressive.