F5 as Authoritative DNS. Arround 2000 zones

The DNS backend for F5 DNS/GTM is BIND which, as far as I know, does not have any direct iControlREST API controls.

However, you can managed the BIND server configuration on a F5 DNS/GTM sync group as any other BIND config so if you have access to all the zone files you can simple copy them to one of the F5 devices and trigger and BIND reload.

Or you could script the zone file creation using something like Create BIND9 Domain Zone Configuration File script to create all the zone files first.