You can set Smart Alerts for zones if you log in through the Circle website app. You also have to have a Circle subscription to do that. You paint in the zones you want it to alert, multiple painted zones for alert notifications are availability as well for the same camera.
I had the zones set up with the Logi service, but what I was saying is that the zones you set up do not translate over to the HomeKit integration and as of yet there is no way to define zones with HomeKits motion detection implementation.