Preheat oven to 350 degrees F (175 degrees C). Grease sides of a 10x15-inch jelly roll pan.
Mix flour, 1 3/4 cup sugar, and 1/2 teaspoon cinnamon together in a large bowl. Cut in butter with a fork to make a crumbly dough. Measure out 1/2 cup of the dough and reserve.
Press 1/2 dough firmly into the bottom of the jelly roll pan to form a crust.
Bake in the preheated oven until golden, about 10 minutes.
Combine 3/4 cup sugar, lemon juice, 1/2 teaspoon cinnamon, and nutmeg in a large saucepan. Add sliced zucchini. Bring to a boil, stirring constantly, until zucchini begins to soften. Stir in reserved 1/2 cup dough. Cook and stir until mixture thickens, 3 to 5 minutes.
Spread zucchini mixture over the crust. Press remaining dough lightly on top.
Return to the preheated oven and bake until top is lightly browned, 35 to 45 minutes. Let cool before slicing into 24 bars, about 20 minutes.