MacOS make etc/resolv-conf use secondary dns or rotate
The /etc/resolv.conf file is not used for configuring the system resolver, like you would probably be used to on other systems like Linux.
However, the configuration you're trying to make is actually not an ideal one - far from it. You're trying to fix a broken DNS resolver by rotating requests between two different DNS servers. This will add extra time to most name lookups, as well as generate unnecessary errors that for will give you problems with some programs.
The best way to solve this is to change your Bind server to do recursive lookups for your internal clients - either by handling them by itself or by forwarding the recursive queries to your ISPs names server.
In either case you want to limit recursive lookups to your internal clients. This can be done via adding an access-control list to your named.conf configuration file that specifies what you consider internal, like this:
acl internal { 
  localhost;
  localnets;
  192.168.0.0/24;
}

This assumes that your local computers have IP-addresses in the 192.168.0.1-192.168.0.254 range. Adapt as necessary.
If you want the server to handle recursive queries by itself, you'll to add the following to the options part of your configuration:
 options {
   recursion: yes;
   allow-query { internal; };
 };

If you want to forward the queries to your ISPs name servers, do it like this instead:
 options {
   recursion: yes;
   allow-query { internal; };
   forwarders {
      1.2.3.4;
      5.6.7.8;
   };
 };

You'll want to replace 1.2.3.4 and 5.6.7.8 with the actual IPs of your ISPs name servers.
Remember to reload or restart bind after making changes to the configuration file.