Yeah, per the above comment, the ZD in redundancy should always have an option for manual failover. They swap pretty quick anyways, so you could always pull the primary and everything would come up really quick on the secondary. .
I've got the failover working with our secondary ZD. Our plan is to relocate what was our Master ZD to a new office. This location will not have any IT staff onsite, so we would like to promote the secondary to Master and create a new failover ZD.