Hi David,
Manually booking directly in TMS, i.e. Booking pages, you can use the Video Conference Master drop-down list
to determine which system should drive the conference (i.e. MCU1 for IP zone A or MCU2 for IP zone B). And TMS also has some logic when selecting that EP and it is based on capability.
But the best way is to use a Conductor as it is built for this purpose and much more.
regards, Ahmad