The "Zone 2 Shift" button works like the Shift key on a computer keyboard. If you hold it down while selecting any other function on the remote control, the command only applies to the second zone at that moment. So you can, for example, make the second zone louder or quieter, or have radio (tuner) output on it while the TV is playing on zone 1. This can also be done conveniently via the app, where the two zones are displayed as two separate amplifiers.

Gut

Thank you very much 👍

The 7100 even has a 3 zone that is operated in exactly the same way.