To prepare a white castle and zucchini casserole casseroles recipe, first you will need to prepare the ingredients. First, preheat the oven to 375 degrees F (190 degrees C). Then, slice the zucchini in half lengthwise and cut each half into 1/4-inch slices. Place the slices in the bottom of an 8x8x2-inch casserole dish. Pour the cream of mushroom soup into the dish and stir to combine. Next, add the shredded cheddar cheese and mix until the cheese is melted and the mixture is evenly distributed. Sprinkle the top of the casserole with grated Parmesan cheese. Bake for 45 to 50 minutes or until bubbly and golden brown. Serve with sour cream.