iPad volume doesn't mute for Zoom or Houseparty

It appears that the volume on my iPad can't be completely muted when using an app like Zoom or Houseparty. I lower the volume using the buttons on the side, but it won't go to zero. I swipe down to get to the controls and drag the volume bar all the way to the bottom and even click on the ringer to silence notifications, but the volume from zoom or Houseparty won't silence completely. Now, I understand this may be an odd thing to want, to go to zero on a conference that you don't want to leave, but there are times when I've wanted to do this. For example, doing a family Zoom the other day we had two separate iPads in the same room on the conference so that we could have the cameras on more than one person, but really wanted to the audio to only come out of one device to prevent an echo effect. Or maybe you're in a Zoom and get a call and want to temporarily turn the volume off completely, but not log out of the conference. But as far as I could see there is no way to do this. This seems to be a feature and not a bug! Am I missing something? (iPad 6th generation, iOS 13.3.1)