In a large skillet, heat the olive oil over medium-high heat. Add the garlic and saute for 30 seconds, then add the zucchini and the mushrooms. Saute, stirring often, until the vegetables are tender and most of their liquid has evaporated. Season to taste with salt and pepper.
Meanwhile, cook the pasta for about 2 minutes less than indicated on the package directions. Drain and return to the pot.
Pour the marinara sauce over the drained pasta. Add the cooked vegetables, then toss well to combine the pasta, sauce, and vegetables. (There is no need to heat the marinara sauce first.)
Transfer half of the pasta mixture to a 3-quart casserole dish. Top with half the vegan cheese. Add the rest of the pasta mixture then top with the remaining vegan cheese.
Cover the baking dish with aluminum foil and bake for 15 minutes. Then remove the foil and bake, uncovered, for 15 more minutes or until heated through and the vegan cheese is melted.
Storing and freezing:Leftovers can be refrigerated for up to 5 days and reheated in the oven or microwave. Or freeze individual portions in glass oven-proof/microwave-proof containers with lids. Defrost the frozen container in the refrigerator overnight before reheating.