Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish with olive oil.
In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the chopped onion and minced garlic, cooking for about 2 minutes until the onion is translucent.
Add the 1 pound of ground turkey to the skillet, breaking it into smaller pieces and cooking for 5-6 minutes until it's no longer pink.
Stir in the diced tomatoes, 1 teaspoon of Italian herbs, ½ teaspoon of salt, and ¼ teaspoon of black pepper. Let simmer for 3-4 minutes.
In the prepared baking dish, layer half of the sliced zucchini, followed by half of the turkey mixture, and half of the mozzarella. Repeat the layers.
Bake uncovered for 30-35 minutes or until the edges are bubbly and the cheese is golden brown.
Allow the casserole to cool for about 5 minutes before serving hot.
Notes
Store leftovers in an airtight container for up to 3 days. For freezing, wrap tightly and it can last for up to 3 months.