You can't add both CNAME and TXT to the same subdomain

I was a bit surprised to learn about this while processing the request of a customer.

Here is the reason why

"If a CNAME RR is present at a node, no other data should be present; this ensures that the data for a canonical name and its aliases cannot be different. This rule also insures that a cached CNAME can be used without checking with an authoritative server for other RR types."