Can Zwift control speed and or inclination of my treadmill?

Zwift doesn't control the speed or the inclination of no treadmill.

BUT with QZ you can!

How?

on Windows: just download the windows version of QZ and then, thanks to the OCR technology, QZ will adjust speed and incline based on your workout! Then you just need to enable the setting in QZ under the Zwift menu, to enable the right scenario (workout, free run, climb portal).

More info about the installation here: https://github.com/cagnulein/qdomyos-zwift/issues/1581#issuecomment-1660774335

on Android, iOS: you have to add your zwift credentials in the settings (requires QZ version 2.16.30) for auto inclination on free run. you have to use the meetup workaround (for QZ version < 2.16.30) for auto inclination on free run. Check this for more detail https://www.youtube.com/watch?v=KTQ2n7yeDbo On workout, you need to load the ZWO file of the workout in QZ also, then QZ will set the speed and inclination!

Requirement: Your treadmill must have speed/inclination control on firmware. In order to do so, check with the QZ app if you can change the speed/inclination using the plus buttons on the speed/inclination tile