i always thought that that would be a nice idea, i like to switch to my headphone zone. but it is doable now without stopping playback. in playing now drag one zone to the other. both zones will playback the same with a small silence but continuing the music. now when you want to stop the first zone unlink (rightclick on link) and stop the first zone. that is how i switch between speakers and headphone zone.
bit more work then a hotkey, but still.
gab
edit.. i was just thinking.. maybe there are mcc commands for linking and unlinking.. then it could be done with a bat file=hotkey. if the coffee starts working ill take a look, that would be sweet.
edit 2.. was an important typo in the post... and there are no mcc commands for so that is a pity. there is something in the automation to link zones, but not to unlink them.