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 external5-apne1-prd-elb-bb8209ae955bc4a4.elb.ap-northeast-1.amazonaws.com is not the root of its zone.
Instead, try zone transfer on elb.ap-northeast-1.amazonaws.com .
Instead, try zone transfer on elb.ap-northeast-1.amazonaws.com .