The error message is the full answer. Your domain must be pointing to ns1.infinityfree.com and ns2.infintyfree.com to create a new account. If it isn’t, even if the domain is pointing to the same nameservers but with different names, you cannot add the domain.
This also goes for adding domains to existing accounts if they have an if0 username.
But, if you have an account with an epiz_ username, you cannot use the infinityfree.com nameservers, and must use epizy.com nameservers instead.
Alternatively, you can use ns1.byet.org and ns2.byet.org instead. Those nameservers always work.