I bought a box of 500 55gr zmax .224 bullets a few months ago since they were cheaper than the Vmax of the same weight. They shoot no different out of my rifles.
But that could be a real old VMax vs a new ZMax may e they changed a bit? I'm not sure. I know Hornady advertises the AMP jacket on the ZMax and not on the VMax.
But...Hornady tells me, via phone, there is no difference.