Even though it's possible, as Monnat states above, it's a solution that is a Bad SolutionTM.
You will have two controllers unaware of each other trying to make the best coverage, and once one controller changes a channel og TX power, the other will have to adjust, making and endless loop of channel adjustments.
You will at least have to register the AP's on the opposite controller as 'known rogue devices'.
You will also have to live with the fact that the ZD1100 will stay on old firmware, including the possible vulnerabilities that brings to some of your network.
That said, I would use another solution for setting this up:Make sure each controller is on a separete VLAN for the AP management.Make sure that VLAN is native/untagged on the ports for the AP's it has to manage.
Trunk/tag the VLAN you SSID is on to all AP's.
Then add the settings Monnet state above, just to be sure.
Hope it helps..