We pick l.root-servers.net, one of the 13 root servers (1), and ask it about xn--r8jz45g.xn--zckzah and learn that xn--zckzah is delegated to four name servers (2), so we ask b.iana-servers.net and get the following answer:
The two IP numbers 2620:0:2830:230::10 and 199.7.85.16 together
All of the one host names that point to IP group 2 use only the mail server idn.icann.org.
The two IP numbers 2620:0:2830:230::10 and 199.7.85.17 together
All of the one host names that point to the two IP numbers 2620:0:2830:230::10 and 199.7.85.17 together, hereafter referred to as "IP group 3", use only the mail server idn.icann.org. Worth noting is that one of the domains that only use the mail server idn.icann.org point to IP group 3.
The two IP numbers 2620:0:2830:230::10 and 199.7.85.15 together
All of the one host names that point to the two IP numbers 2620:0:2830:230::10 and 199.7.85.15 together, hereafter referred to as "IP group 4", use only the mail server idn.icann.org. Worth noting is that one of the domains that only use the mail server idn.icann.org point to IP group 4.
The mail server idn.icann.org only
There are eleven domains that only use the mail server idn.icann.org.
One of those point to IP group 3. Worth noting is that all of the host names that point to IP group 3 use only the mail server idn.icann.org.