I am curious how this went for you. I have been bombarded with zoom problems and they always seem to be mikrotik customers. I have tried disabling sip alg and udplite but it still seems like I get a lot of complaints from my customers at sites where I am running mikrotik routers and waps.
Today I found that zoom won't even connect it just hangs at the negotiating phase, where it displays "connecting". Both tested on a customers iphone and a laptop - and then the customer tried again at home and it worked fine. I worked with this customer through remote desktop verifying this. So something seems to be wrong with mikrotik and zoom but I havn't had a lot of time to spend on it.
I really don't know but I am pretty sure zoom have enough infrastructure to overcome basic sip alg vendors compatibility issues.
I know that theoretically it's possible for a MikroTik setup to have such a scenario like you described but, it works for me.
It might be a site or a setup specific issue.
In any case of mangle rules first try to bypass them for the specific clients and destinations to make sure it's not a FW or routing rules issue.