rhf,
to be true, I always wonder about the meaning of the "ZV" acronym, me too ;-)
As far a I know, that is used by Saudi Aramco (look for their Material System Specification n° 64-SAMSS-634 about "Local ZV Control Systems"), for example.
If the Z pertains to position, most control valves are now available with HART or communicating positioners that include diagnostics such as hysteresis and changes over time.