Actually, the video you need to watch is this one. It perfectly explains the process of creating DHA, how to test that you have. However, one point to raise, I've improved the process with trial and error. Once you have watched the video, you are welcome to apply the following change to the process to improve the taste and increase the amount of vitamin C in the solution. I used this when a family member was diagnosed with cancer, with dramatic results, to the point that the doctors doubted their own diagnosis within a week!
The change to the process I made is to blend the courgette skins first, then juice the pulp. Once the oxidization process in the video is complete, I froze the liquid. When you defrost the liquid, you find that you end up with a pure clear liquid and the solid green courgette separated , the liquid will contain the majority of the Vitamin C, and you can decide whether to remix the pulp and drink together, or if this is unpalatable, you can decant the clear liquid containing the majority of the DHA and drink this in any other juice or water. Its quite a sharp, tart taste simply because of the concentrate of Ascorbic Acid in the small amount of liquid, but I managed to oxidise about 60grams of L-Ascorbic Acid in about 2 pints of liquid, which lasts about 2 days. Because the DHA is 95% absorbed by the GLUT1 cells, there is no impact on the bowel that I have seen. With normal high dose Vitamin C, you will experience a loose bowel because you are only absorbing a low % of the Vitamin, what you cannot absorb is passed through. With DHA, almost all the Vitamin C is absorbed very quickly into the blood.
Hope you found this useful.