I own https://www.DomainDetect.io https://www.DomainDetect.io, we pull new domains from Zone files/3rd party sources daily. ~200,000-400,000 domains per day to

I own https://www.DomainDetect.io https://www.DomainDetect.io, we pull new domains from Zone files/3rd party sources daily. ~200,000-400,000 domains per day to alert on new phishing sites for businesses. So we do something similar. I would start with something like https://czds.icann.org/en https://czds.icann.org/en attempting to resolve them asyncronously in your country, then work your way through the new daily additions. Use an ElasticSearch/Cassandra backend for speed to query that volume of information. Your problem will come from the countries/TLD's that dont play ball with their zone files. These are trickier to obtain.