If you’re facing error 1004 on cloudflare while adding the mailchimp DKIM cname, to verify for your domain name, follow this tutorial.
When we add the new cname, the “orange cloud” is automatically selected when it’s being added. Uncheck the orange cloud icon and then the add button won’t give error 1004 on cloudflare.
There is no need to buy pro version as suggested by some tutorials, to disable cname flattening. The issue is not related to that.
The only issue was that the cloudflare was adding it as proxied through cloudflare server. By disabling it, the cname will not use cloudflare as proxy anymore.