Place zucchini halves in large saucepan and weigh them down with small plate. Cover with boiling water. Simmer over low heat 6 to 8 minutes or until almost tender. Drain and refresh zucchini under cold water.
With spoon, scoop pulp from zucchini, leaving 1/4 inch border all around. Chop pulp coarsely and drain in sieve. Invert zucchini boats onto paper towels to drain.
Remove and discard sausage casings, break up meat; saute in heavy skillet over moderate heat 5 minutes. Add onion, parsley, basil and marjoram; cook until onion is soft, about 5 minutes; stir in zucchini pulp. Remove from heat and stir in bread crumbs, egg, 2 tablespoons cheese, salt and pepper.
Preheat oven to 350°. Fill zucchini boats with stuffing. Place in baking dish. Sprinkle with remaining cheese and bake 35 to 45 minutes, until lightly browned.
Variation on a Greek classic.