Cook sliced zucchini for 5 minutes in boiling salted water. Combine soup, carrots, sour cream, onions, water chestnuts, and mushrooms. Lightly fold zucchini into mixture. Add chicken and cheddar cheese. Mix melted butter with stuffing mix. Spread all but 1 cup stuffing mix in a 9 x 13 inch pan. Put mixture over stuffing. Cover with remaining stuffing and bake at 350 Fahrenheit for 45 minutes.