There is an excellent article over on FanGraphs trying to identify the next Kyle Hendricks. You know, a guy who seemingly has below average stuff, a weak fastball with a low strikeout rate...but with great command.
Here is the link http://www.fangraphs.com/blogs/finding-the-next-kyle-hendricks/
I look at Zach and get the comparison to Hendricks. But I am reminded more of Greg Maddux. His slight stature, below average velocity and his reliance on breaking balls and command. Maddux made a Hall of Fame career living on and mostly off the corners. I never saw a pitcher get more called strikes off the plate than Maddux. He earned those strike of course because that's exactly where he expected the ball to finish up. His catcher sat out there and never moved his glove. It took years of success before the umps routinely called those pitches off the plate as strikes.
Obviously Zach won't get the umpires to give him those calls on a regular basis. Those are reserved for future HOF'ers. But as he gets more established, he may begin to stretch their zone too. Pitch framing and consistently hitting his spots will help influence the zone. Getting batters to chase a pitch 1 inch further outside can be the difference between a long fly ball out and one that doesn't come back.
Command pitchers aren't as sexy and not usually as desired as guys who can throw in the mid to upper 90's. But those who know how to keep batters off balance with excellent command can perform at an All Star level. I'm not suggesting that Zach will be the next Greg Maddux, but I think it's possible for him to be a very good MLB pitcher.
For now, I'd be happy if he were the next Kyle Hendricks.