Obviously HVAC zoning needs to be defined here so that all understand the term.
There are basically three different ways that zoning can be applied to a home. For example, a home could be zoned with equipment. This means you could have two - or more - completely separate comfort systems, each with an air conditioner, a furnace and a thermostat. One system might supply conditioned air to a downstairs area, while the other system handles the upstairs area.
Or a home could be zoned with controls and dampers, using a single comfort system. In this case, a home could be divided into as many as eight areas or “zones,” with each zone having its own sensor that monitors the temperature and controls it with a motorized mechanical damper.
The third way is simply a combination of these two methods with two or more systems, each zoned with controls.
So, a home with two Heat Pumps, HVAC systems independantly controlled, has at minimum 2 zones.