I believe it even says in the zoner ID that they are not immunize to piracy. It is at the pirates discretion on whether or not he wants to put up with the zoner. So technically the pirate has every right to kill a zoner if he refuses to give up the goods (be sure to give an engagement notice). But as to what Quorq said, that pirate should not go and land on a zoner base if he had just attacked a zoner.