The Zoom desktop client uses ultrasonic sound to detect its proximity to a Zoom Room or another device joined into the meeting. In addition, the Zoom Desktop Client will automatically disable computer audio to prevent audio echo in a Zoom Room.
Since Zoom Rooms are the audio source, the Zoom Desktop Client will automatically disable computer audio (both speaker and microphone audio) if it detects proximity to a Zoom Room. You do not have to do anything if this feature is enabled.