Didn't Mel Kiper have Taylor listed as number 5 for senior (or other) quarterbacks? Pretty sure i saw something like that. I don't know if i would go as far as heisman contender, but he should have a great year. I don't see why he couldn't have all big 12 numbers.
Defenders drop picks, receivers drop touchdowns, it happens both ways.
The fact is that Zac will have a more experienced line in front of him, a better core of receivers to catch the balls, and another year with a tough system. He should be improved, and have a better statistical year. I expect nothing less.