• Preheat the oven to 350°F. Grease and flour a 9×13-inch rectangular cake pan. You can also use nonstick baking spray (the kind with flour).
• Whisk salt, baking powder, baking soda, cinnamon, cocoa, and flour in a medium bowl. Set aside.
• In a large bowl, whisk eggs until beaten, then whisk in oil, vanilla and both sugars. Whisk until well combined.
• Using a spatula, stir the dry ingredients into the wet ingredients until just combined. Stir in zucchini.
• Spread batter evenly in prepared pan. Bake for 35-40 minutes or until a toothpick inserted in the center comes out clean and the top springs back when lightly pressed.
• Let the cake completely cool before removing from the pan and frosting.

To make the frosting:

• Whisk cocoa, salt, and powdered sugar (sift if the cocoa is lumpy).
• Add butter to a large bowl or the bowl of a stand mixer fitted with the paddle attachment and beat until creamy.
• Add powdered sugar cocoa mixture and mix until crumbly; add vanilla.
• Add enough cream to make the mixture come together; beat at least 1 full minute before adding more cream to desired consistency.