Only way to measure it is by recruiting rankings and draftees to NFL and multiple AAC teams and other G5 are beating you at both.
ZW appears to be a transcendent talent that lifted meh talent around him to be competitive in 3 of 5 P5 games (2 weren't competitive) and to dominate, at times, G5 competition.
If true, this bodes well for ZW, but says without ZW BYU is solidly a G5. Maybe not even high G5.