Cook noodles according to package directions, drain. In a large bowl, combine the noodles, tuna, zucchini, sour cream, celery, onion, mayonnaise, mustard, thyme, oregano and salt; mix well. Spoon half into a 2 quart baking dish coated with nonstick cooking spray.
Sprinkle with half of the cheese mixture. Repeat layers. Top with tomato. cover and bake at 350*F. for 30-35 minutes. Uncover; bake 5 minutes longer. Yield: 6 servings.