I was wondering if it is possible to map certain services on different eth interfaces with freepbx/pbxact.
I have a pbxact system with 2 ethernet port connected to different network. I would like to put the zulu on eth0 en the rest on eth4 for different routing.
Not directly. You can set up all of your services to use specific IP address ranges and use the Linux networking routing rules to do what you want, though.
Which service in particular? You can bind the Apache instance to a specific IP and port, and you can also bind the sip drivers to specific IP and port. You can also do it for TFTP, SSH, the SQL database instance and probably some other ones too. You would need to do it manually though, not through the GUI, and then modify the corresponding configuration, so the services that need to connect to other services know how to do it. Consider that doing such thing might break service integration, you need to do some reading.