Preheat your oven to 375°F (190°C) and grease a 9x9-inch baking dish.
In a large bowl, mix together the cornmeal, flour, baking powder, baking soda, salt, pepper, and sugar.
In a separate bowl, whisk together the buttermilk, eggs, and melted butter.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Fold in the grated zucchini, shredded cheddar cheese, corn kernels, and chopped green onions.
Pour the batter into the prepared baking dish and smooth the top.
Bake for 25-30 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Allow the casserole to cool for about 10 minutes before serving. Enjoy!
