Zucchini and cucumber seeds are vegetables that both use a little fermentation to help in saving the seeds. When saving them you’ll want as mature of a fruit as you can get. Even after you harvest them it can help to let them cure for a couple days before cutting them open. It’s still a strange feeling to stop eating the favorite plants of a crop and let them grow out for seed. Maybe the pleasure is in the hope it gives to next year.
For zucchini start by cutting off any “neck” that is only flesh and doesn’t contain any seeds. Then carefully with a good knife cut the first half inch or so or around the perimeter of the vegetable so it can be pulled apart into two halves. The reason for this procedure is to prevent throwing a knife straight through the seed cavity and slicing a handful of them.
Next, scoop out the seeds.
Or thumb out the seeds.
The seeds will have a thin coating around them. To remove that place the seeds and anything stuck to them into a container and cover it with water. Add a cover to keep the flies out and ferment for 1-2 days. Caution not to forget about the ferment for too long as it can eventually begin to deteriorate the seeds germinating potential.
After the light fermentation the seed should be free from their covering. Check to make sure then you can stir up the seeds in the water, the good seeds should sink to the bottom and you can pour the rest off the top. This can be repeated by adding more water, stirring, and pouring until the seeds are generally clean. Then drain, rinse, and dry the seeds in a warm, dry place, and mix them up periodically to keep it going evenly.