Question
How do I address the following error?
Error: domain.tld. already has a CNAME record. You may not mix CNAME records with other records.
Answer
Canonical Name (CNAME) records create an alias for another domain name, which DNS resolves. This is why you're unable to mix CNAME records with other records.
If the other record is needed more than the CNAME record for your domain, the existing CNAME will need to be deleted before you're able to create the needed record. You can delete the CNAME record at WHM >> DNS Zone Manager or the account's cPanel >> Zone Editor.
You can view details on the WHM >> DNS Zone Manager and cPanel >> Zone Editor at the respective links provided below.