What horrible acronym/concept are those.

It seems to be a US thing: https://en.wikipedia.org/wiki/Partial_zero-emissions_vehicle

> In California, PZEVs have their own administrative category for low-emission vehicles. The category was made in a bargain between automakers and the California Air Resources Board (CARB), so that automobile makers could delay making mandated zero-emission vehicles (ZEVs)—battery electric and fuel-cell electric vehicles.