Source IP F5 DNS Zone Forwarder

You need think why you want to do this first?

You have a self-ip in the same range as the Listener/DNS virtual server and by having the correct routing the F5 will use it and it then if you have SNAT automap the source ip will be that self-ip.

EDNS0 Implementation and Troubleshooting recommendations

Other than that nowadays DNS should utilize EDNS "Insert Source Address into Client Subnet Option" Overview of the DNS profile (14.x and later) as the client ip is what the end DNS servers should be interested off.

Also better use Wide IP configurations and what can't be resolved by the wide IP will be send to a DNS pool under the listener. That is the better way for me as without health monitors and with Generic hosts it is like Zonerunner/Bind.

Overview of DNS query processing on BIG-IP systems

How does the BIG-IP GTM/DNS decide on a DNS response

BIG-IP DNS Configuration