Combine flour, sugar, cinnamon and salt. Cut in butter until crumbly, set aside 3 cups. Pat remaining crumb mixture into the bottom of a greased 13x9 baking pan, Bake at 375 for 12 minutes.
For filling, put zucchini, lemon juice in a saucepan and bring to a full boil. Reduce heat, cover and cook for 6-8 minutes or until crisp tender. Stir in sugar, cinnamon and nutmeg, cover and simmer for 5 minutes. (Mixture will be thin)
Spoon over crust and sprinkle with the reserved crumb mixture. Bake at 375 for 40-45 minutes until golden.