Preheat oven to 350 degree F. In a large mixing bowl combine shredded zucchini, summer squash, and salt. Let stand 15 minutes. Place mixture in colander and squeeze to drain. In same bowl combine beaten eggs, snipped parsley or parsley flakes, garlic, chopped onion or dried onion, fresh dill or dried dillweed, and pepper. Stir in squash mixture and feta cheese. Spoon mixture evenly into an ungreased 13x9x2-inch baking pan.
Cut phyllo sheets in half crosswise. Lightly brush a sheet of phyllo with some of the melted margarine or butter. Place phyllo sheet on squash mixture. Top with another sheet of phyllo. Brush with more margarine. Add remaining phyllo, brushing each sheet with melted margarine. With a sharp knife score through phyllo, making 16 squares. Bake for 50 to 55 minutes or until a knife inserted near the center comes out clean. To prevent overbrowning, cover strudel with foil the last 10 minutes of baking. Let strudel stand 10 minutes before serving. Makes 16 side-dish servings.