01 - Preheat oven to 400°F. Lightly grease a medium baking dish with cooking spray or a small amount of olive oil.
02 - Heat 1 tbsp olive oil in a large skillet over medium-high heat. Season chicken pieces with salt, pepper, and smoked paprika. Sauté for 4–5 minutes until lightly golden but not cooked through. Transfer to a plate and set aside.
03 - In the same skillet, add remaining olive oil. Sauté onion for 2 minutes until softened, then add garlic and cook until fragrant, about 30 seconds.
04 - Add zucchini and sun-dried tomatoes to the skillet. Cook for 3–4 minutes until zucchini begins to soften. Stir in spinach and cook until just wilted. Remove from heat.
05 - In a bowl, combine heavy cream, oregano, basil, chili flakes (if using), half the feta, and half the mozzarella. Season with salt and pepper and mix well.
06 - Arrange sautéed vegetables and chicken pieces in the prepared baking dish. Pour cream mixture evenly over the top.
07 - Sprinkle with remaining feta, remaining mozzarella, and all the Parmesan cheese, distributing evenly across the surface.
08 - Bake for 25–30 minutes until chicken is cooked through and the top is golden brown and bubbling. An instant-read thermometer should register 165°F when inserted into the thickest piece of chicken.
09 - Let the dish rest for 5 minutes before garnishing with fresh basil leaves and serving hot.