If squash is cooked, then use less broth and let it cook down till it forms a creamy consistency. (thecuriouscoconut.com)
I'm sure frozen zucchini would work — though you might want to add less broth in that case since the zucchini will probably have absorbed more moisture by being frozen. (avocadopesto.com)
I used 1 cup less broth because I like a thicker soup but the flavor was spot on! (theglowingfridge.com)