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I've been playing it as units entering a ZOC must attack. 7.0 Procedure states, "Whenever a Friendly unit moves into an Enemy-controlled hex, the Friendly Player is required to attack all Enemy units exerting a ZOC into that hex." Therefore, if they start the turn in enemy ZOCs, they do not have to attack but have the option to disengage. However, I'm not 100% sure if I am playing it correctly or not.
Got some feedback on Facebook from the SPI gurus in SPI fan page community. you are indeed correct and for once I played correctly!
Thanks for the assist.