I noticed that when I'm in a Zoom online meeting, and have audio playing on my computer (i.e. a YouTube video), everyone in the meeting can hear it with crystal clarity. I tried to do a test meeting to figure out what's happening, and as it turns out, the audio is heard even when my headset microphone is unplugged. That means it's not the microphone picking up the sound coming from the headphones. Both are part of the same headset, and are connected with 3,5 jacks.
In case it can help, at least one of the jacks on the front panel has recently broken, and now requires me to insert the cable multiple times, otherwise the headphones make a lot of weird noises, which can, apparently, also be heard in Zoom meetings.