The flower of zucchini and other summer squash are quite edible and have become regular fare in Mexico and other Third World countries. Native Americans who grew winter squash before Europeans arrived made squash blossom soup.

The reason squash blossoms became food so early was that these plants bear two kinds of flowers, one for each sex, on the same plant. There are roughly three male pollen bearing flowers for each single female ovary flower. Since the female flowers are the fruit bearers, indigenous people began plucking the excess male flowers to eat before the crop of squash matured. This was particularly useful with winter squash that takes all season to mature compared to summer squash which makes edible fruit in just a few weeks after pollination.
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The link below connects to some great photos of how fresh picked squash blossoms are used in a particular fiesta dish in Oaxaca, Mexico
Zucchini flowers, with the baby female fruit attached are now expensive and upmarket vegetables in restaurants, certainly in australia and U K. The flowers can be stuffed with a rice and minced meat filling or a delicate cheese mix. They are often presented stuffed and deep fried in very light Japanese style batters. (When you stuff them, it's a delicate amount and then you'll find you can close the petals and give the ends a very gentle twist at the end tips, to keep them closed but it's a delicate operation).