In my E46, the HVAC always turned on (albeit low) whenever I turned on the car.

The only way to have it not do so is to have the dealer turn reprogram the car to keep it off at start. To me, it wasn't worth the $100 reprogram just to save me a single button press.

With the ZRC, it's in the back, so reaching back there to turn it off is a hellavualot more inconvenient.

So, ZRC remembers the last setting.