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 ip-080-069-099-155.um20.pools.vodafone-ip.de is not the root of its zone.
Instead, try zone transfer on um20.pools.vodafone-ip.de .
Instead, try zone transfer on um20.pools.vodafone-ip.de .