In a large saucepan, over medium-low heat, cook and stir zucchini and lemon juice for 15-20 minutes or until zucchini is tender. (I cook mine in the microwave.) Add sugar, cinnamon and nutmeg; simmer one minute longer. Remove from heat and set aside.
For crust, combine flour and sugar in a bowl; cut in butter until mixture resembles course crumbs. Stir 1/2 cup into zucchini mixture.
Press half of remaining crust mixture into a greased 15x10x1-inch baking pan. Spread zucchini mixture over top; crumble remaining crust mixture over zucchini. Sprinkle with cinnamon.
Bake at 375°F for 35-40 minutes or until golden and bubbly. Top with ice cream or whipped cream to serve, if desired.