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 u46xqka6t2keiko6hxet22fq6hixl6b7tu4hb3ciqoz6p7c4iwaa.mx-verification.google.com is not the root of its zone.
Instead, try zone transfer on google.com .
Instead, try zone transfer on google.com .