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I think the reason there not releaseing a zanizibar demo is becuase they have no time becuase from all the moutain dew palyer info and from e3 we know almost everything about zannzibar so they would probally release it exept for there would be no time and the only source that most everyone would get it would be oxm
Or because they don't want to. But your idea is good too.
According to weekly update its because they don't have time to do it.