Some European airlines officially prohibit nested tickets in their terms&conditions. A nested ticket is if you book A -> B on ticket 1, then B -> A -> B on ticket 2 and again B -> A on ticket 1. I do not know if EK has any official rules against it. Even if they had, the likelihood of EK going after you is extremely small.

If you nest the ticket with the ticket of another airline, there is nothing anybody can do against it, anyways.