Apex domains cannot have CNAME records.
Question and response
Question
dig zadns.co.za. NS
Answer
zadns.co.za. 3 NS ns3.mydnscloud.com.
zadns.co.za. 3 NS ns2.mydnscloud.com.
zadns.co.za. 3 NS ns1.mydnscloud.com.
zadns.co.za. 3 NS ns4.mydnscloud.com.
Authority
The response has no authority records.
Additional
ns1.mydnscloud.com. 3 A 102.214.10.93
ns2.mydnscloud.com. 3 A 102.213.4.245
ns3.mydnscloud.com. 3 A 102.67.141.157
ns4.mydnscloud.com. 3 A 102.214.8.251
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0