I have heard of someone on this board who mixes ozonated water with lemon and trace minerals. I personally don't mix it with anything because ozone is oxidative, meaning that it will attempt to oxidize and therefore neutralize any foreign matter. The reason it does not harm healthly living cells is because we have anti-oxidant enzymes that prevent that from occuring. But the minute you mix something with ozone, it will go to work oxidizing that substance. That's the same reason you should drink it on an empty stomach. The goal is to have it enter into your GI trac and blood stream where it can go to work on toxins in the body. In my opinion it would be counter productive to mix something with it (unless you have found information to the contrary). For example, a good case could be made for mixing MSM with ozonated water because the MSM helps the body to utilize it. Yet, I still take these separately, just in case.
With Vitamin C in particular, yes, they should most definitley be taken separately, with several hours between. Vitamin C can be used to counter-act a strong detox reaction from ozone. So, they have an offsetting effect from one another.