AFAIK this is because Zoom is optimised for speech. Theres quite a few different options you can select to make this better - background noise suppression should be off, “original sound” should be enabled, and I also think that arguably the “optimise for video clip” should be selected too.
However its very likely you’re not going to get much better quality than you are. My awareness is that Zoom prioritises network stability over fidelity and thus compresses things in an uncontrollable way. I’ve also seen a lot of people using Zoom for streams etc, and all I can say is that I think it’s a terrible medium. From speaking to others, the only use-case for it is to minimise the slightly technical aspect (especially on a Mac) of getting audio into OBS or SL OBS.
Sounds like you’ll need to go with it, in which case you may need to tailor very specifically what sort of audio you’re putting through it (ie not a huge amount of dynamic range!)
