These are my Zucchinis (Sure Thing), in my greenhouse. One of the plants exhibited a white film on the plant leaves, while the rest did not. Since posting the plant has nearly doubled in size, and seems to be healthy. Not to mention its starting to put out some female flowers (not opened yet), and I water the plant every single day, good and deep. If i miss a day, especially if it gets hot (~ 30-35 celsius), the plant wilts a little on the large leaves. My night temps are about 12-15 celsius in the greenhouse. Average day is 20-25 celsius.
I've asked about the white on my leaves as well because I was concerned about powdery mildew issues. So far Im not noticing anything wrong with the plants ability to produce or grow. Not is it showing any signs of disease other than the white filmy leaves.
web link to the discussion on mine.. I had responses that helped me understand what it was. Maybe its not the same as your issue, but hopefully it helps.
https://www.helpfulgardener.com/forum/vi ... 0&start=45
Thought I'd share my experience with my zucchinis this year so far. Hopefully you get some zucchinis! OR even just a few flowers so you can eat a some zucchini flower fritters! mmmm.