You will need to kill techno-thieves until they drop the prototype rocket. Once it drops, this task will be completed
They are CL86
Once both of the tasks are complete, your quest will update.
Now Destroy the Rebel Commandos
Now we send a message to those who would attack an Imperial ship. The squad of Rebel Commandos who shot down the transport have been located. Eliminate them!
You will be given a waypoint to a squad of Rebel commandos. You need to kill nine of them and the quest will update
They are CL84
Return to Captain Thrawn
Return to Captain Thrawn at the Emperor's Retreat.
Head back to the Emperor's Retreat on Naboo and speak to Captain Thrawn.
Captain Thrawn: Well done. I do not impress easily. I don't expect the Rebels to think twice before shooting down another transport, but I will make sure they pay dearly whenever they do. Colonel Veers feels the same. You should speak with him.
This completes the quest. Speak to Colonel Veers, right next to Captain Thrawn to get the next quest.
Colonel Veers: I have a mission for you. Infiltrate a Rebel base on Talus for information about the Rebel destruction of the Death Star.
You: Yes sir. Colonel Veers: The Rebels will pay for the loss of so many Imperial lives.