I use the macOS TR and Zwift apps simultaneously on an extended monitor. (My MacBook Pro is off in my periphery during the workout.) I currently use TR in minimized mode and fill the remainder of the screen with the Zwift app.
I would like to use each app in its own full-screen mode so that I can keep the TR app in my periphery for reference but have the instructional and workout step notification text notification on my primary screen. The MVP would be the ability to send instructional text and workout step change notification text to another screen. Ideally, a full feature implementation would include full customization of app element displays on each monitor. (E.g. Time, heart rate, and cadence on one monitor; power and the workout graph on another.)