Yes, it is possible to configure two default routes (0.0.0.0/0) on a MikroTik router for each of your internet services and then use routing rules to direct traffic from certain users through a specific service and traffic from the rest of the users through the other service.

To achieve this, you must first configure the two default routes on your MikroTik router, assigning the appropriate gateway for each internet service. You can then use packet marking rules or routing rules based on source or destination IP addresses to identify user traffic that you want to route through a specific service.

For example, you can mark certain users' traffic with a specific flag and then create a routing rule that directs traffic with that flag to the default route corresponding to the desired service. Meanwhile, traffic that does not meet the marking criteria will be automatically routed through the other default route.

It is important to note that the specific configuration may vary depending on the network topology and exact requirements, so it is advisable to consult the MikroTik documentation or seek specialized assistance if you need help with the precise implementation of these configurations.