Preheat oven to 350°. Spray an 8x4-inch loaf pan with baking spray with flour.
For streusel: In a small bowl, whisk together flour, granulated sugar, brown sugar, and salt. Add melted butter, and whisk until mixture is crumbly.
For bread: In a large bowl, whisk together flour, granulated sugar, baking powder, baking soda, and salt. Stir in zucchini.
In another small bowl, whisk together buttermilk, melted butter, and egg. Pour over flour mixture; stir just until moistened. Spoon batter into prepared pan. Top with streusel.
Bake until a wooden pick inserted in center comes out clean, about 50 minutes. Let cool in pan for 10 minutes. Remove from pan, and let cool completely on a wire rack.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/zucchini-streusel-bread/