In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until it becomes translucent.
Add the minced garlic and cook for an additional 1 minute, stirring frequently to prevent burning.
Increase the heat to medium-high and add the ground turkey. Cook until browned, breaking it apart with a spatula, about 5-7 minutes.
Stir in the diced zucchini, Italian seasoning, salt, and black pepper. Cook for another 5-6 minutes until the zucchini is tender.
Add the diced tomatoes and stir to combine. Let it simmer for an additional 2-3 minutes.
If using, sprinkle the shredded mozzarella cheese on top and cover the skillet for 2 minutes, allowing the cheese to melt.
Remove from heat and garnish with fresh basil if desired. Serve warm.