SO you want anything that is not a WideIP hitting the GTM to be resolved from your backend DNS servers? Are they performing recursion for the traffic or are they authoritative?
If this is the case you have two options:
1.)My personal preference - Setup DNS Express as an authoritative slave for your backend zones. https://support.f5.com/kb/en-us/solutions/public/15000/500/sol15585.htmlconfig1. If you need recursion for any reason you could enable it in the GSLB settings, but if it is a public facing GTM I wouldn't recommend that.
2.)You can configure you listener with a pool containing you backend LDNS servers to handle the resolution with DNS cache enabled in you DNS profile.
I will highly discourage everyone from resolving from BIND locally. If you ever want to use zonerunner locally to host zone, you should always setup DNS Express to be the resolver. Local BIND is single threaded and resolves from disk not memory.