Spray a 7x11-inch casserole dish with cooking spray and preheat the oven to 350 F.
Combine the shredded zucchini, onion, corn, bell pepper, and eggs in a large bowl.
Mix in half of the shredded cheddar cheese, paprika, oregano, celery salt, salt, and pepper.
Add the muffin mix and stir to combine.
Spoon the mixture evenly into the prepared baking dish and top with the remaining cup of shredded cheddar.
Bake for about 1 hr or until the top is lightly brown and a toothpick inserted in the middle comes out clean.