ftld.zabbix.net has no NS records.
NS records for this zone are defined at zabbix.net.
NS records for this zone are defined at zabbix.net.
Question and response
Question
dig ftld.zabbix.net. NS
Answer
The response has no answer records.
Authority
zabbix.net. 1800 SOA ines.ns.cloudflare.com. dns.cloudflare.com. 2397400229 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0