To direct a subdomain to third-party NS, do the following:
Check with the owner of the third-party NS to which you want to direct the subdomain for their addresses.
If the domain settings already contain records like A
for a directed subdomain, remove them
For each of the third-party NS addresses add a new entry
with the following data:
Wait for the update DNS cache
... This usually takes several hours (maximum 72).
Make sure that the subdomain has been added and configured on the specified NS and the necessary DNS