That particular C. moschata under many names has become quite a fad as a zucchini substitute. Other butternuts are also usable as zuke substitutes. One other option as a zucchini substitute is the Cucuzzi/Italian squash/Tasmanian Bean... which is a gourd (Lagenaria siceraria)

With the exception of the bitter C. pepo gourds, I think you can use pretty much ANY very young squash as a summer squash. I've eaten MANY a young butternut as summer squash, I don't like wasting produce and always use the young squash this way in the fall when I do the final cleanup and pull the vines. Once cooked up, they all taste more or less the same, although some are firmer and others more watery.