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

In a large skillet, heat a tablespoon of olive oil over medium heat. Add the chopped onion and minced garlic, sautéing them for about 2 minutes until the onion turns translucent.

Add the ground turkey to the skillet and sauté for 5-6 minutes, or until the turkey is no longer pink and lightly browned.

Stir in the drained diced tomatoes, dried Italian herbs, salt, and black pepper into the skillet. Allow this mixture to simmer for 3-4 minutes.

Layer half of the sliced zucchini at the bottom of the greased baking dish, followed by half of the turkey mixture and half of the mozzarella cheese. Repeat the layers.

Place the assembled casserole into your preheated oven and bake uncovered for 30-35 minutes until the cheese is bubbly and golden brown.

Allow the casserole to cool for about 5 minutes before serving for easier portioning.