GB rate is nice and could conceivably be a way for someone to be decent without missing bats. See guys like Brett Anderson or Brad Keller.
Zeuch's stuff seems to be below average across the board but some of it is kind of tantalizingly close to being average or better. He'd need to gain one or two mph on his average and top end fastball to have Brad Keller's, for example. Ivan Nova was a durable and worth owning shitballer for many years but he was sitting 92.5 or 93 and touching 96, which is better than Zoinks. When you see a thinner 6'7" guy, it's easy to imagine them adding velocity (but if Zeuch could he probably already would have...)
Zeuch has consistently limited runs in the minors and has avoided being destroyed in the limited MLB sample, so that's a tiny feather in his ball cap.
He's a boring up and down depth SP right now, like Waguespack, but he has the chance to tweak a couple of things and elevate his profile. He probably won't do that though; remember that we are talking about best case scenarios when referencing guys like Nova and Keller and there is a 90% or 95% chance he doesn't work out like them.
By tweaking things I mean adding a full letter grade to his FB, turning his boring changeup into a plus pitch, refining his used cutter into a weapon - stuff like that.
In the current depth chart I don't see how they can justify rolling him out there as an MLB SP. There are tons of guys ahead of him who don't need such drastic developments.