This doesn’t sound that bad. Unless I’m misunderstanding something, the ERP was used as a source of truth for DNS records, and that mechanism broke. There’s no indication of actual data loss so it should still be in the ERP DB, and it’s a matter of reverse-engineering how it was all put together and then extract the data into a zone file (or into a managed DNS service such as Route 53) at least for the core domains w…
I would be looking at the Internet Archive and Whois too figure out some basic domains and what the registrars are and go from there but of course depends on what business they are in and what their domain names were doing.