I just recently finished watching ZZ in hopes that it would provide some more impact to CCA, but it really didn't do much. The series is underrated and by the end it is an enjoyable series, but I don't think it's necessary to watch pre-CCA. It doesn't really give that much more background to the importance of Axis like I'd hoped it would. That said, watch it if you can. If you can get past the first 15-20 episodes it does become watchable and enjoyable.