My favorite thing to do with zucchini and yellow squash is just to straight-up grill them. I slice them into planks (or heavy bias) and toss them in a bit of olive oil and S&P and then straight onto a direct grate setup. By the time the outsides are marked (only flip once or you'll make a mess) the inside will be nice and tender.

I like them just like that, but occasionally get a bit fancier. I'll cool them off, roll them up with some goat cheese and then top with a little smoked tomato sauce with toasted puya chiles or drizzle with balsamic vinegar and sprinkle on some fresh herbs and maybe a bit of Parmesan.