Preheat oven to 350 degrees F (175 degrees C). Grease a 2 quart casserole dish.
In a large saucepan over medium-high heat, cook zucchini in lightly salted water until crisp-tender, about 5 minutes. Drain, and place in a large bowl. Stir in the condensed soup, sour cream, onion, and carrots.
In a small bowl, mix together stuffing and melted butter. Spread half of the stuffing mixture in the bottom of the casserole dish, add a layer of the zucchini mixture, and top with remaining stuffing mixture.
Bake for 20 minutes in the preheated oven, or until the top is golden brown.