Zucchini plant question
This looks like choanephora rot, a common fungal disease that is promoted by wet weather during bloom. The fungus first infects flowers and then moves into the young fruits. Aside from spraying preventatively with a fungicide the best thing to do is remove blossoms from the ends of fruit once they begin to enlarge- after pollination and fertilization of ovules (baby seeds) has occurred. There are no resistant cultivars.
Here is more on our website https://extension.umd.edu/hgic/topics/choanephora-rot