I suspect this issue is more related to the Mikrotik RoS itself so you’ll probably get better help at forum.mikrotik.com.
Just a suggestion, feel free to provide some more details about you installation, for example config (/export), a simlple network diagram, ip addresses, subnets etc. This will make easier for forum users to understand your problem and help you out.
Here are some useful articles regarding ZeroTier and MIkrotik RoS: