Zucchini and other cucumber relatives have separate male and female flowers. The male flowers are attached to slender stalks. The female flowers sit on the end of the swollen ovary, which later becomes the fruit. The female flowers must be pollinated with pollen from the male flowers for fruits to set. Usually bees serve as the pollinators. It there is not much bee activity there may be little fruit set. Bees are sensitive to some types of insecticides, especially some formulations of Sevin.

First check your plant to see that there are some female flowers on it. Usually the first flowers to form are males. Later both male and female flowers are produced. If there are not both male and female flowers there is no chance of fruit yet. If you have both male and female flowers on the plants and fruits are still not forming you may need to hand pollinate the female flowers. You can do this with a small paintbrush like a watercolor brush. Simply swirl the brush inside the male flower to pick up some of the pollen, then swirl the brush inside a female flower to transfer the pollen to the pistil, the rod-like protrusion in the middle of the flower.

Additional information on hand pollination of squash can be found in this fact sheet:

http://edis.ifas.ufl.edu/hs398