So you will build a structure with the response fields within. So if your UDF has these values as a stream forward them to the substructures.
If this stream has only one payload (complete return) then you might use two message mappings in row. E.g.
MM1 Request + Bulk-Response
MM2 Target-Payload of MM1 and sort the right values to the correct Worker-IDs
What have you tried?
Kind regards
Konrad