Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente, about 9-11 minutes.
While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat.
Add the sliced zucchini to the skillet and sauté for 5-7 minutes, stirring occasionally, until the zucchini is tender and lightly golden.
Add the minced garlic and red pepper flakes to the skillet with zucchini and cook for 1-2 minutes until fragrant, stirring frequently to avoid burning.
Drain the cooked pasta, reserving 1/2 cup of the pasta cooking water.
Add the drained pasta to the skillet with the zucchini and garlic mixture.
Add the remaining 1 tablespoon of olive oil, 1/4 teaspoon salt, black pepper, and lemon zest to the pasta and zucchini. Toss to combine well.
If the pasta seems dry, add reserved pasta water a few tablespoons at a time until desired consistency is reached.
Remove from heat and stir in the grated Parmesan cheese, chopped basil, and parsley.
Serve immediately, garnished with additional Parmesan and fresh herbs if desired.