The Truezone system uses regular thermostats for each zone. They can be single stage stats, or multi stage - the zone panel can be configured to work with either type. Thus it has the standard terminals (HZ432 as an example) - RH, RC, W1, W2, W3, Y1, Y2, G, O, B, DS/BK. It has a built in fossil fuel kit for heat pump/gas furnace combinations.
The Envirazone system uses networked thermostats - the IAQ stat - without the need for the IAQ interface module. The zone panel only has 3 terminals for each zone thermostat - 1, 2, 3. It also appears that the Envirazone panel W8835 doesn't have an integrated fossil fuel kit for use with heat pump/gas furnace combinations. You would have to add a separate kit for that if needed.