How do I make Firefox grant permission to use the microphone but not the camera?

When I use Web apps like Zoom in Firefox, I get a single permission prompt asking for both the camera and microphone. My response there either grants both or denies both. How can I grant the microphone permission but not the camera permission? I tried allowing both at first, then going into the site’s permission list and hitting the X by the camera permission to remove it, but that removes the microphone permission too, even though they’re listed separately with their own X buttons.