I just got them too. The way I understand it is that you don't want your muscles to get use to the same exercises, so you add maximize in for variance when that happens just to shake things up. I would switch them out once you got comfortable with shape up and kinda know what to expect, or if you stopped getting sore.
Then switch to maximize to "confuse" your muscles so they don't know what to expect. Do those for awhile and then go back to shape up. Have you read the book? You know to do front, back, rest, front, back, cardio, then rest.