"Everyone knows that ISIS is a zionist saudi group" - This, as I must assume you know, could not be further from the truth. It wouldn't be hard to prove me wrong though. You just have to provide some objective evidence that most people around the group view ISIS as a pro-zionist group. Every sliver of evidence out there about the group points to the opposite, especially their recruiting tactics, which are public record.
Further, it is not at all unusual for Muslim Extremists to kill their fellow Muslims when they make agreements with whom they consider to be enemies of Islam. So, what evidence do you have to support your belief that ISIS is a pro-zionist movement?