The answer to 'why is my zone control system blowing hot air' is that there is likely an issue with the thermostat, dampers, or the control system itself. Zone control systems use multiple thermostats and dampers to regulate airflow and temperature in different areas of your home. If one of these components is malfunctioning, it can cause hot air to blow in the wrong zones.
Some common causes include a thermostat that is not properly calibrated, a damper that is stuck open or closed, or a problem with the central control panel. This can lead to uneven heating, with some rooms getting too much hot air while others stay cold.