Preheat your oven to 190°C (375°F). Lightly grease a round baking dish or an oven-safe skillet with a small amount of olive oil.

Heat the olive oil in a skillet over medium heat. Add the sliced zucchini and halved cherry tomatoes. Season with garlic powder, salt, and black pepper. Sauté for 3–4 minutes, stirring gently, until the vegetables begin to soften.

In a mixing bowl, whisk the eggs and milk until smooth and well combined. Add the shredded mozzarella, grated Parmesan, and chopped parsley. Mix gently to distribute the cheese and herbs evenly.

Arrange the sautéed zucchini and tomatoes evenly in the prepared baking dish or skillet. Pour the egg mixture over the vegetables, ensuring everything is evenly covered. Transfer to the oven and bake for 20–25 minutes, or until the center is fully set and the top is lightly golden.

Remove the frittata from the oven and let it cool for a few minutes. Garnish with fresh parsley, slice into wedges, and serve warm.