Zucchini usually have male flowers first then later the female flowers come and eventually they get in synch. Unfortunately, if you do not have good pollinator insects, no fruit will set and grow.
It’s important to understand that zucchini and other squash plants are monoecious, meaning they produce separate male and female flowers on the same plant. While these flowers may look very similar at first glance, there are some distinct differences once you take a closer look. The most obvious differences are the small immature fruits at the bases of female flowers and the long thin stems of male flowers. Early in the growing season, squash plants tend to produce more male than female flowers. While you may have tons of flowers, in order to produce fruit you must have both male and female flowers at the same time. Bees and other pollinators are usually responsible for transferring pollen from the male flowers to the female flowers, which ultimately leads to fruit development. If there are few bees in your garden, you’ll likely have poor pollination and fruit set. Bees are sometimes few and far between in urban areas. If you think this is the case in your own garden, you can try playing the role of a bee yourself by hand pollinating the flowers. The pollen of squash plants is very sticky and is formed in the center of the male flowers. You can try using a small paint brush to move some of the pollen from the male flower to the stigma of the female flower. If that sounds too tedious, you can also just remove the male flower and gently roll its pollen onto the stigma of the female flower. It’s best to try hand-pollination early in the morning as squash flowers open early and only last for one day. Also keep in mind that squashes can only be fertilized by their same species. A zucchini cannot be pollinated by a winter squash and vice versa.