Changes since SOA version
IXFR is a zone transfer request that returns changes since a specific SOA version. Enter the SOA version to request changes since then.
Not an apex domain
The domain 2001-1ae8-2-4860--12.ip6.tmcz.cz is not the root of its zone.
Instead, try zone transfer on ip6.tmcz.cz .
Instead, try zone transfer on ip6.tmcz.cz .