I do it as follows (don't have it with me, so will go by weight work):
Day 1: circuit/back
Day 2: interval/chest
Day 3: lower body (to give the shoulders a break and not work them 3 days in a row)
Day 4: shoulders and whatever
Day 5: biceps (to not double up on triceps, which are synergists for shoulders)
Day 6: triceps
Day 7: rest/stretch
This makes the most sense to me: going from largest to smallest muscle group, not doing circuit (which has leg work in) back-to-back, and allowing recovery for muscles that are synergists for others.
One thing to watch out for: CTX cardio is heavy on the step and plyo moves (5 out of 6 workouts have plyos in, and 4 out of the 6 have step). You may want to change some of the high impact moves to low impact (I did in kickboxing and Interval, but still had to limit my rotation to 2 1/2 weeks because my knees didn't like it).