Bring a large pot of salted water to a boil and cook spaghetti until al dente. Reserve 1 cup pasta water before draining. Heat olive oil in a skillet over medium heat and fry zucchini slices until golden. Remove half for garnish. Add garlic and basil to the pan. Add cooked spaghetti and gradually add pasta water while tossing. Stir in grated cheese slowly until the sauce becomes creamy. Season with salt and pepper. Top with reserved zucchini and extra cheese before serving.