Hello Pieter,
since each ZD is 1106 and without buying additional licenses, there is no way you can have them as one network.
Configuration wise they can be same however 6 AP will go to specific ZD and other 6 AP's to other ZD. This is doable and can reside in same network.
in this type of setup, you can't have smart redundancy either, so is limited ZD discovery won't work either as both have same licenses and no capacity to handle more AP than 6.