Add the baking soda, natural unsweetened cocoa powder, and salt to the bowl and mix well.
1/2 cup unsweetened cocoa powder, 1 1/2 teaspoons baking soda, 1 teaspoon salt
Add the properly measured all-purpose flour and stir just until no white streaks remain. The batter will be very thick at this stage
2 cups all-purpose flour
Turn the zucchini onto a paper towel, gather it up, and squeeze out as much liquid as you can. Measure out exactly three cups and stir it into the batter.
Stir in one and a quarter cups of the chocolate chips. Spread the thick batter evenly into your prepared pan, then sprinkle the remaining quarter cup over the top.
1 1/2 cups chocolate chips
Bake for 25 to 30 minutes, until the top loses its shine, small cracks start at the edges, and the center no longer jiggles when you nudge the pan. Cool in the pan for at least 45 minutes before slicing, longer if your kitchen is warm.
Squeeze the zucchini as dry as you can, and measure your three cups after squeezing, not before. Pull the seeds as you shred, and skip the peeling.
Use natural unsweetened cocoa, not Dutch-process. The baking soda needs the acid in natural cocoa to react with. Read the ingredient line, since natural says cocoa and Dutch-process says processed with alkali.
If the batter worries you before it goes in the pan, let it sit five minutes after you add the zucchini, and it will loosen on its own.