Hello, good people!
This is the first time I'm trying to grow anything and I was really happy how my 7 zucchini plants were developing, even started spotting some small zucchinis growing when 2 days ago this started appearing:



At first it was only on a couple of plants and now it spread on all of them and really started devastating them.
I saw some kind of small flies on the bottom side of leaves and even sprayed them with some kind of insecticide but today my plants are in even worse shape than yesterday...
I really got fond of these plants because that is the first time I ever tried something like this and it was very fulfilling watching them grow from seed.
If there is anything I can do to help them, it would really mean a lot!
Thanks anyway!

I'd have to guess powdery mildew in your case, but white spots, sort of evenly distributed over the zucchini leaf surface is what's called natural silvering, which is a genetic trait. Many treatment options for the former. Just look online.