Heat oil in a large skillet over med heat.
Add onion and cook, stirring occasionally, until soft, about 6 min. Add garlic and cook, stirring frequently until its fragrant, about 2 min.
Add zucchini, cover skillet and cook, stirring occasionally until crisp-tender, about 5 min.
Add tomatoes and cook, covered for 2 min.
Stir in basil, and season with salt and pepper.
Cover and cook for 1 minute
Add 2/3 of Parmesan to the mixture and stir.
Sprinkle the remaining cheese on top and serve hot.