Only zones that are part of a ZoneSwitch rule set are involved.
In other words, if you setup ZoneSwitch to switch between "HDMI" and "S/PDIF" zones, it will have no impact on playng to a third, fourth, etc. zone like "My DLNA Device".
Also, you would only use ZoneSwitch if you need automatic zone routing. If you just have a local zone and a DLNA zone, there's probably no reason.
I wanted to use the ZoneSwitcher for this: When I start MC (after an upgrade, for instance) the DLNA zone is not immediately available and I have to manually switch after a while to the DLNA zone player view to have music played to that zone by double clicking on files etc. I thought I could route all audio media to the DLNA zone and then manually select play to if I once in a while wanted to sample an audio file on the Player.
If I set ZoneSwitcher to [Media Type]=[Audio], play in DLNA zone AND stop playback in Player, all audio media is sent to the DLNA zone (as expected) but I cannot manually Send to Player, i.e. even if I Send to Player the music is played in the DLNA zone.
Since you said that "zones that are part of a ZoneSwitch rule set are involved" but not others I removed the stop playback option in ZoneSwitcher so that only the DLNA zone is involved/mentioned in the ZoneSwitcher settings. But now audio media is sent to the Player if the Player is active when double clicking, i.e. the ZoneSwitcher no longer routes all audio to the DLNA-zone and I experience no difference from how it was before the ZoneSwitcher was introduced (and yes, the ZoneSwitcher is enabled).
I might have misunderstood something. I just wanted to report the behaviour I see in case it is not intentional, and explain my intended use for the new feature (which I understand the feature is not really intended for).