In a large bowl, beat together the coconut oil, eggs, honey and vanilla. Coarsely grate the zucchini, measure 2 cups and then remove the excess moisture by either pressing it between two paper towels or squeezing a fistful of zucchini at a time over the sink. Put the zucchini in the bowl and stir the ingredients together until well combined. Add the flour, cocoa powder, salt, baking powder and cinnamon to the bowl; stir together until just combined. Next, fold in the chocolate chunks and walnuts.
Spread the batter in an 8- or 9-inch-square baking pan that’s been lined with aluminum foil and sprayed with nonstick cooking spray. Be sure to allow the aluminum foil to hang over the ends of the pan so the excess foil can be used as handles to remove the bars from the pan later on.
Bake the brownies in a 350°F oven for 25 to 30 minutes or until a toothpick inserted into the center comes out mostly clean. Allow the brownies to cool completely and then carefully lift them out of the pan using the foil as handles. Set the brownies on a cutting board and use a sharp knife to cut them into squares. Brownies can be stored at room temperature in an airtight container for up to 5 days.