Preheat the oven to 350°F. Line a 9-inch square baking pan with parchment so that the ends hang over by about 2 inches on opposite sides. (If you want thinner brownies, use a 9-inch by 13-inch dish.)
Place the avocado, applesauce, coconut sugar, syrup, and vanilla in the bowl of a food processor and blend until smooth. In a large bowl, mix together the flour, cocoa powder, baking soda, and salt. Stir in the zucchini and fluff and separate with your fingers so it doesn't clump together. Add the chocolate chips and do the same things. Pour the avocado mixture into the bowl with the dry ingredients and mix gently until everything is just barely combined: overmixing will yield a tough brownie.
Scrape the batter into the prepared baking pan and smooth out the top. Transfer to the oven and bake for about 25 minutes, until the edges are just barely pulling away from the pan and the center is set, but still a bit soft. The brownies will firm up as they cool: they should be slightly undercooked.
Remove from the oven and allow to cool for at least 15 minutes. Cut into squares and serve warm or chill and serve later.