ESPN created "Total QB Rating" that they created in 2011 and have been modified since. An "analytics" approach if you will. Mentioned this earlier in the season and Zach was in the middle of the pack. Since it didn't list Zach up near the top, many didn't appreciate it. He's a true Freshman, expected him to be very good this early is expecting too much.
Right now
Zach has a QB rating of 49.7. 90th out of 133 QB's. Tua Tagovailoa, ALA is 1st at 97.5 and Kyler Murray, OKLA is 2nd at 96.9.
Interestingly enough,
Morgan is ranked 88th at 49.8. It's not a question of ability, it's a question of health.
http://www.espn.com/ncf/qbr/_/page/2
Here's a partial explanation of the formula:
What Total QBR Captures
In particular for college football, we introduce this year the Total Quarterback Rating, also known as Total QBR or QBR. And, since college football has imbalanced schedules, QBR will be seen in both a form that adjusts for defenses faced - often called Opponent-Adjusted QBR or Adjusted QBR - and in a form that doesn't adjust for defense, often called Raw QBR or Unadjusted QBR.
The scale of QBR is from zero to 100, where 50 is average. Top quarterbacks are in the upper 80s and 90s for a season. Manziel, in fact, ranked first in QBR in 2012 with a value of 90.5. His unadjusted value was 86.4, also the best among FBS schools. The increase from unadjusted to adjusted reflects that he did face good defenses overall.
Unlike NCAA Passer Efficiency, which uses only box score statistics, Total QBR accounts for what a quarterback does on a play-by-play level, meaning it accounts for down, distance, field position, as well as the clock and score. A 5-yard gain on third-and-4 is a good play, whereas a 5-yard gain on third-and-14 isn't. A 20-yard touchdown pass when tied in the second quarter means more than a 20-yard touchdown pass when down 30 points late in the fourth quarter. QBR accounts for those things using analysis that turns traditional productivity into points on the scoreboard and wins in the standings.
It also accounts for a quarterback's ability to scramble, his ability to run on designed rush plays, how well he avoids sacks, drawing and committing penalties, and all-important fumbles, which can be significant for quarterbacks...
http://www.espn.com/college-football/story/_/id/9612585/total-quarterback-rating-college-football