FMG same policy base for two gateways

[MERANA]

I have a new firewall policy with specific zones. Now I have to add my secondary DC firewall to FMG but have to use the same policy base for both firewalls. Problem is i have a to add more config to existing primary firewall policy base so that i can push same policy to both firewalls. 

2nd DC firewalls have interfaces configured in the policies and as i have to merge that to existing policy of primary dc firewal which is configured to use zones, now I am not sure how to do it? 

Just to summaries the issue:

Primary DC firewall: Policy imported to FMG configured to use zones instead of interfaces.

secondary DC firewall: Need to add 2nd dc firewall config to priamry DC firewall but how to marge and create zones? 

when new zones created on the FMG can this automatically be updated to policy base? 

Please can someone help answering my query ?