spfext.zapproved.com has no NS records.
NS records for this zone are defined at zapproved.com.
NS records for this zone are defined at zapproved.com.
Question and response
Question
dig spfext.zapproved.com. NS
Answer
The response has no answer records.
Authority
zapproved.com. 900 SOA ns-1071.awsdns-05.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0