Are green squash the same as zucchini?

No. Although both are green and of similar shapes and sizes, they belong to different species of squash. Green squash are also called "summer squash" and generally refers to a broad category of squash that are harvested and consumed when immature, while zucchini is a specific variety of summer squash. Also known as Italian squash or courgette, zucchini belong to the Cucurbita pepo species.