Cook the pasta according to the package directions. Drain and return it to the pot.
Meanwhile, heat the oil in a skillet over medium-high heat. Add the walnuts and cook, stirring frequently, until beginning to brown, 3 to 4 minutes.
Add the garlic and cook, stirring frequently, until beginning to brown, about 1 minute.
Add the zucchini and raisins and season with ½ teaspoon salt and ¼ teaspoon pepper. Cook, tossing occasionally, until the zucchini is just tender, 4 to 5 minutes.
Add the zucchini mixture to the pasta and toss to combine. Sprinkle with the Parmesan before serving.