Preheat the oven to 325 degrees F (165 degrees C). Spray two 9x5-inch loaf pans with cooking spray.
Make the bread: Mix sugar, zucchini, oil, eggs, and vanilla together in a large bowl. Stir in raisins.
Combine flour, baking soda, salt, cinnamon, and baking powder in another large bowl. Whisk flour mixture into zucchini mixture; stir until almost all lumps are gone. Divide batter between the two prepared loaf pans.
Make the topping: Whisk brown sugar and cinnamon together in a small bowl until well combined. Sprinkle over batter in the loaf pans.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 1 hour. Cool in the pans for 10 minutes, then remove from the pans and finish cooling on a wire rack.