Bring zucchini, lemon juice, sugar, nutmeg, cinnamon, and salt to boil, reduce heat and simmer till tender.
Mix remaining ingredients separately to form a doughy mixture.
Stir 2/3 cup of the doughy mixture into zucchini filling and allow to simmer for 5 more min. Divide the remaining doughy mixture in half.
Press half of the doughy mixture into 9X13 inch ovenproof pan, a round pie plate or a baking dish to form the crust.
Spread the zucchini filling into pan or pie plate, evenly.
Top entire pie with other half of doughy mixture, crumbling with fingers as you add topping to cover the zucchini filling. (if you prefer topping to be more crumbly, you may want to add 2-3 additional tablespoons of flour and mix well, before sprinkling on top)
Bake at 350 for 40-50 minutes or until golden brown.