Preheat your oven to 350°F (175°C). Lightly grease a 9×13 inch baking dish.

**Prep the Zucchini:** Place sliced or shredded zucchini in a colander. Sprinkle with 1 teaspoon of salt and toss. Let sit for 20-30 minutes. Rinse lightly, then squeeze firmly with hands or paper towels to remove as much water as possible. This step is crucial to prevent a soggy casserole.

In a large mixing bowl, combine the drained zucchini, chopped onion, and shredded carrots.

In a separate smaller bowl, whisk together the sour cream and the lightly beaten eggs until smooth. Pour this mixture over the vegetables.

Add the shredded cheddar, grated Parmesan, 1/2 teaspoon of salt, and black pepper to the large bowl. Mix everything until well-combined.

**Prepare the Topping:** In another bowl, combine the dry stuffing mix with the 4 tablespoons of melted butter. Toss with a fork until the crumbs are evenly moistened.

Pour the zucchini mixture into the prepared baking dish and spread evenly. Sprinkle the buttery stuffing mix over the top.

Bake for 30-35 minutes, until the center is set and the topping is golden brown. Let rest for 10 minutes before serving.