GTM should answer for all public Websties

I have GTM connected internet, But i have limited zones as master for internal websites, also I want this GTM should answer for all public dns Quries

like google.com, but i dont want to add pool to listeners !

I have mentioned DNS bind servers as forward Ip in nameid configuration?

but no idea how it will take for all public zones that is not mentioned in zone list and wide IP .

should i do any changes on GTM to answer the DNS requests and take data from DNS bind internal (not via Pool members)servers?