Heat olive oil in a large skillet over medium heat. Add zucchini and garlic to the hot oil. Use tongs to turn zucchini and garlic to coat with oil, about 30 seconds. Stir in spinach and cook 2 minutes. Add basil, sunflower seeds, salt, and pepper and cook until softened, about 2 minutes. Transfer to a large platter and drizzle with extra-virgin olive oil before serving.