BYU had played comparable, or even easier, schedules in the past and few and far between were the QBs who threw the ball as well as Zach did. Consider:

In 2020, the opponent W/L % was .483, but Zach's passer rating was 196.44 w/ 8 games above 200.
In 2017, the opponent W/L % was .494, but BYU's team PER was 106.56 w/ 0 games above 200.
In 2016, the opponent W/L % was .475, but Taysom's PER was 115.71 w/0 games above 200.
In 2011, the opponent W/L % was .428, but BYU's team PER was 130.58 w/ 1 game* above 200 (Nelson 2nd half vs USU & 1st half vs Idaho St)
In 2006, the opponent W/L % was .469, but Beck's PER was 169.05 w/ 4 games above 200.
In 2001, the opponent W/L % was .435, but Doman's PER was 153.14 w/ 2 games above 200.
In 1997, the opponent W/L % was .483, but Feterik's PER was 144.10 w/ 0 games above 200.
In 1989, the opponent W/L % was .458, but Detmer's PER was 172.90 w/ 3 games above 200.
In 1984, the opponent W/L % was .396, but Bosco's PER was 150.96 w/ 1 game above 200.
In 1980, the opponent W/L % was .424, but McMahon's PER was 175.65 w/ 5 games above 200.