Hi, in (shipment) output determination there is only 1 IDOC message type + partner possible for 1 (shipment) output possible.
This can be solved by sending the (shipment) message to your own logical system by ALE.
Then when the IDOC is received in your own system it can be distributed to the final destination logical system('s) by ALE.
To create a shipment IDOC message that is to be send to your own logical system make a copy of the shipment outbound process message (SHPM, ....) and change the ALE processing flag to 'Processing with inbound trigger'. When you now create a shipment IDOC it will be distributed to your own logical system.
Then in the partner profile for your own logical system in inbound processing choose the inbound process code ED08 (Forward IDOC). Now when you receive the IDOC it will be distributed (by the ED08 process code) to the logical system('s) as defined in the distribution model for this shipment message.
Regards Jack