Wash and scrub zucchini well and cut into thin round pieces. Combine flour with half the salt, pepper and oregano in a bowl. Coat zucchini slices in mixture. Heat oil in a skillet and saute' zucchini until brown. Place zucchini in a greased baking dish and top with tomato. Combine sour cream and the rest of the salt, oregano and pepper and spread over tomato slices. Bake 30 minutes at 350 degrees.