The most common winter squash are Cucurbita maxima, Cucurbita moschata and Cucurbita pepo. They will not cross with each other but maxima will cross with other maxima, and so on. Cucurbita pepo are also your summer squash, so a winter pepo will cross with your summer pepo. Cucumbers are Cucumis sativus usually, but some cucumbers are Cucumis melo (which are also some of your melons) Same goes here, they wont cross with each other but different sativus will cross and you cucumber melo can cross with your melon melo. Cucurbita and Cucumis won't cross with each other. Sorry, probably too much info, lol
