I don’t think you can do this with a “secondary controller”. ZWave allows multiple controllers, but a secondary controller infers that it’s on the same network, and then you’re still limited by the 4 hop issue back to the primary controller.
If I understand correctly, you really want a second controller - ie on a second network - that is connected back to OH via IP? I’m not very familiar with Z-Way, but it it runs over an IP network (which I think it does?) then it should allow you to do this.