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 uther.lfhk.cuni.cz is not the root of its zone.
Instead, try zone transfer on lfhk.cuni.cz .
Instead, try zone transfer on lfhk.cuni.cz .