Zucchinis are very similar to cucumbers. While they taste a bit different, they are both long green fruits. The zucchini just has stemmy bit on the end. It is actually a type of squash.
Zucchinis are only “fruits” in the botanical sense of being the fruit of the plant however. Zucchini is a botanical fruit because it is formed from the ovary of the zucchini plant. Even more specifically, it is a pepo, a type of botanical berry! This is again only a scientific classification that is irrelevant to the ordinary person. It just means that it was formed from a single ovary and has a wholly fleshy wall. If you include zucchinis in your berry mix, you are weird and should stop it.
For practical purposes zucchinis are vegetables. Despite the name of their botanical classification, they are a vegetable culinarily and not a fruit or berry. They have a “vegetably” flavor and are not sweet. They are not eaten in fruit salads; they are eaten in regular salad or savory dishes, often cooked. These are hallmarks of being a vegetable.