From: Phaedrine Stonebridge

ell my zucchini have a gazillion blooms but I have had only one
zucchini so far! I have never had this happen before and have not
really had pollination problems before. But could this be the problem?

Well it takes two to tango so you must have both boys and girls blooming at the
same time--then there has to be an agent to take the pollen from the boys to
the girls,normally bees--but if there are not enough bees then you have to do
it. Often one sex will appear first and nothing will happen until the other
arrives so there may be a period of bloom of one sex only so check the sex
situation