I can't say I feel the recoil is less than the M4gery, the muzzle climbs as much as a regular AR, but then I have no scientific proof either way. As to parts, if you have an FNC among those that have ARs, you'd be in the same predicament, at least ZM is in the US and you won't have to be at parts dealers' mercy. As to firing the AR with its stock collapsed, while it's true you'll have access to all the controls, your face might not agree with it when it's at risk of being hit by the rear sight or scope during recoil
. ZM's stock needs to be lifted to be folded, but to unfold it, you just swing it back without having to do anything else.
Aren't folding/collapsible stocks designed for space saving? If that's the primary concern for ZM's folding stock, I think it's achieved its objective, without the convenience of being fully operational while folded, again this is not new, FNC and Galil both have the same limitation. Being an add-on to an existing system it's forgivable, in the case of FNC and Galil the designers could have done their stocks better.
I think an AR with the collapsible stock is more than adequate for the job, all the shortcomings you gentlemen listed are valid, since there's no perfect system, we all have to live with some compromises.