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 _spf.eu-de-1.cm.net.sap is not the root of its zone.
Instead, try zone transfer on eu-de-1.cm.net.sap .
Instead, try zone transfer on eu-de-1.cm.net.sap .