Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter or cooking spray.

In a large bowl, combine sliced zucchini, onion, and shredded carrots. Season with salt and pepper.

In another bowl, stir together cooked cheese tortellini, sour cream, and cream of chicken soup until combined.

Mix the stuffing mix with melted butter until evenly coated.

Spread the vegetable mixture in the baking dish, top with the tortellini filling, then add the stuffing mix on top.

Cover with aluminum foil and bake for 25-30 minutes. Remove foil and bake for an additional 10-15 minutes until golden brown.

Let the casserole rest for a few minutes before serving.