I assume you have for each datasource loop you have set the target step to the corresponding request. Then if your script directs execution to the first request, the test case will loop until there is no more data, then fall through past the first datasource loop. I think you would put a Groovy script step there with a [tt:18auj795]return[/tt:18auj795] statement.
[tt:18auj795]DataSource
Groovy Script (branching logic to Request1 or 2)
Request1
DataSourceLoop1 (loop to Request1)
Groovy Script (return statement)
Request2
DataSourceLoop2 (loop to Request2)[/tt:18auj795]
