I have the latest Android, version 10. The Bluetooth speaker plays audio fine when the app is the firefox browser but in Zoom, the volume is so low you cannot understand anything.
Also, the person on the other end of the zoom call reports that the sound from the microphone is low volume and distorted.
Check the audio settings in Zoom.
Bluetooth has different protocols for different uses. When you pair two devices, if there is more than one use case possible, they should ask which to use, otherwise they will settle on what seems best. In the case of an audio speaker, it’s likely that straight audio is the only possibility, and this may not suit Zoom very well.
Have you tried using a wired headset? I use the one from the Fairphone shop with good results (it includes a mic so that’s sorted too).
As to the microphone, since the speaker isn’t providing one, the phone will have to choose between mic 1 (at the bottom, used for standard phone calls) and mic2 (at the top, used for hands-free). The choice, I believe, is governed in normal phone calls by “speaker” mode. I suspect the phone will be using mic1 but you’ll be too far, since mic 1 is designed to pick up only sounds from very near.
My short answer is: use a headset, wired is probably best, or no connected device at all, in which case Zoom will presumably choose speaker mode, since hand-held mode makes no sense in a video call