Apex domains cannot have CNAME records.
Question and response
Question
dig zeus.cobol.com.co. NS
Answer
zeus.cobol.com.co. 5 NS hera.cobol.com.co.
zeus.cobol.com.co. 5 NS zeus.cobol.com.co.
Authority
The response has no authority records.
Additional
hera.cobol.com.co. 4 A 164.92.76.14
zeus.cobol.com.co. 4 A 164.92.68.92
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0