Hasn’t been able to or didn’t?
There’s a big difference, and any number of “HEADPHONE Community” members would have happily loaned him theirs (there’s a lot of us) if asked (myself included).
There’s only so much time in the day.
Beyond publishing his own measurements (see various threads, on various forums), Zach has never objected (nor, frankly, even commented as far as I’m aware) on measurements of his headphones done here or elsewhere.
Anyone that buys a set of ZMF cans (and @Resolve owns, as I recall, as set of open Vérité) can publish their measurements of them. Holding that back from “formal reviewers” would be counter-productive.