Preheat oven to 350 degrees F. Line a 9- x 5-inch loaf pan with a piece of foil large enough to hang over edges and spray the foil with non-stick cooking spray.
In a medium mixing bowl, combine flour, baking powder, and salt and set aside.
In a large mixing bowl use an electric mixer to combine sugar, vegetable oil, eggs, and vanilla extract. Add sour cream and orange zest and mix until well combined. Using a wooden spoon, add the dry mixture and stir to combine. Add 1 cup chocolate chips and stir, just until combined.
To make crumb topping place flour, brown sugar, butter, and vanilla extract in a medium bowl and use a pastry blender or fork to combine. Finish by working the mixture with your fingers to be sure it is well combined and crumbly.
Transfer batter to prepared loaf pan and sprinkle with crumb topping and bake for 50 to 65 minutes, or until toothpick inserted in center of bread comes out clean. Remove from oven and immediately sprinkle with 1/2 cup mini chocolate chips. Allow to cool completely in pan. Use the foil edges to lift the cake from the pan and transfer it to a cutting board or serving platter. Dust with a bit of powdered sugar, slice and serve.