The biggest thing I see is what is the business need to maintain two independent databases that appear will share information? Why not operate/maintain everything under ZC?

Affectively would need to establish action at each database to communicate to the other if they are to be simultaneously updated. Either they push to each other or one pulls from the other at the time of need... With one not being a ZC database, would need to know/understand the difference in table/data relationship as compared to the ZC database structure and implement the appropriate relationships/interface functions/ties.