Set your oven to 375°F (190°C) and oil a 9×13-inch baking dish lightly.
In a large bowl, combine the chopped chicken, zucchini slices, halved cherry tomatoes, sliced red onion, and minced garlic. Drizzle with olive oil and sprinkle on the oregano, basil, smoked paprika, salt, black pepper, and optional red pepper flakes. Toss everything together until nicely coated.
Transfer the chicken and vegetable mix evenly into the prepared baking dish, then top with the shredded mozzarella and grated Parmesan cheese.
Cover the dish with foil and place it in the oven to bake for 20 minutes.
Remove the foil and continue baking uncovered for an additional 10 to 15 minutes, or until the cheese is melted, bubbly, golden, and the chicken reaches an internal temperature of 165°F (75°C).
Sprinkle the fresh parsley over the top before serving. Enjoy warm, paired with rice, quinoa, or crusty bread for a filling meal!