I personally don't think vit. C will interfere with CDS enema's. I'd also add that I'm not entirely sure if vit. C interferes with CDS either. I know this was the case with the older Miracle-Mineral-Supplement products. Though if memory serves, I think that was with respect to the chemical reaction(activation process).
On the topic of CDS enema's *which I've never done myself. I'd add that chlorine dioxide enema's will in most cases, cause the mucus membrane within the colon tract to strip away. Which will look much like long strands or parasites(without life of course). And so there's that to consider I guess.
Aside from that, may I ask what condition has brought you to follow such a powerful treatment? Have you considered other treatments? I've been using a combination of blood purification and Colloidal Silver as an alternative to years of Miracle-Mineral-Supplement /CDS therapy. And though, I'm not saying the Miracle-Mineral-Supplement and CDS didn't work in my cases as they were very effective. Though the elimination of taste and various side effects associated with the long term use of Chlorine dioxide treatment was a Godsent in my own case.