Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with olive oil.

In a large mixing bowl, combine chicken breasts, diced zucchini, halved cherry tomatoes, sliced red onion, and minced garlic. Drizzle with olive oil and add dried oregano, basil, smoked paprika, salt, black pepper, and optional red pepper flakes. Toss until well-coated.

Transfer the mixture into the prepared baking dish, spreading it evenly. Sprinkle mozzarella and Parmesan cheese generously over the top.

Cover with aluminum foil and bake in the preheated oven for 20 minutes.

Remove the foil and continue baking for an additional 10 to 15 minutes until the cheese is bubbly and golden. Ensure chicken reaches an internal temperature of 165°F (75°C).

Let the bake rest for a few minutes before serving. Garnish with fresh parsley.