Also, AP discovery prefers "set director ip a.b.c.d" first; then last ZD(s) connected to; then DHCP Option 43 and DNS resolution of 'zonedirector' hostname.
You can SSH to each AP, and specify the desired ZD IP address twice, to tell them
that this one ZD is their target.
rkscli: set director ip a.b.c.d a.b.c.d
*Free Tip: How can I keep an AP in Standalone Mode if there's a ZD on the network?
Answer: Configure "set director ip 22.214.171.124" (or any unreachable IP address).