Bobby's Lighter Creamy Hash Brown Casserole

Preheat oven to 375 °. Spray a 7 x 11-inch casserole dish with nonstick spray. Heat the oil in a large nonstick skillet over medium-high heat. Add the onion and cook, over medium heat, stirring occasionally, until very tender, 6-“8 minutes. Add the zucchini and garlic and cook, stirring until the zucchini is softened, 3-€“4 minutes. Add the flour, stirring to combine. Add the milk, salt, pepper and nutmeg; bring to a boil. Reduce the heat and simmer, stirring occasionally, until the mixture begins to thicken, about 5 minutes. Stir in the potatoes until well mixed. Spoon the mixture into the casserole dish. Combine the cheese, crackers, and butter in a small bowl. Sprinkle over top. Bake, uncovered, until the filling is hot and the cheese is melted and bubbly, about 40 minutes.