Hi @Noltari ,
The core implementation of airzone didn’t have mode controls for slaves: https://github.com/home-assistant/core/pull/67924
Now the buttons are there and when clicked generate an error message: Fix HVAC modes for Airzone slave zones by Noltari · Pull Request #68851 · home-assistant/core · GitHub
It’s much less intuitive now IMHO. Was there a technical issue with the first implementation?