Grease (I use coconut oil) and flour two 8 x 4 inch pans. Preheat oven to 325 degrees F.
Sift flour, salt, baking powder, soda, and cinnamon together in a bowl. Set aside.
Beat eggs, oil, vanilla, and sugars together in a large bowl. Add sifted dry ingredients to the creamed mixture, and beat well. Stir in zucchini until well combined. Pour batter into prepared pans.
Combine oatmeal, brown sugar, flour, and cinnamon in a separate bowl. Add softened butter by cutting it in with a fork until mixture is crumbly.
Add crumb topping 15 minutes into baking. This allows the crumbs to stay on top rather than sinking into the batter.
Bake for 45 to 60 minutes, or until tester inserted in the center comes out clean. Cool in pan on rack for 20 minutes. Remove bread from pan, and completely cool.
