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 b73f7402caeda12bf8e1aae36a4748b9.4d2b1745c2f60b96c0435194c8fdbb89.comodoca.com is not the root of its zone.
Instead, try zone transfer on comodoca.com .
Instead, try zone transfer on comodoca.com .