You want to send a request message synchronously to multiple receivers. The first message received is to be used as the reply message. All messages that are received after this message are ignored.
For this purpose, define a fork and insert one branch for each receiver. For each branch, insert a synchronous send step and define a send context. You use this send context in the receiver determination in the Integration Directory. Define the end condition for the fork in such a way that one branch must have been executed for the fork to be completed.