Preheat the oven to 350°F (180°C). Grease and line a 8-inch (20cm) square pan with parchment paper.
Grate the zucchini finely. Do not squeeze out the moisture, the liquid from the zucchini is important for the texture.
In a large bowl, whisk together the honey, egg, and vanilla.
Add the butter and mix to combine.
Add the grated zucchini and mix to combine.
Add the cocoa powder, flour, baking powder, and salt. Stir just until combined.
Fold in about two-thirds of the chocolate chips.
Transfer the batter into the prepared pan.
Spread it evenly.
Sprinkle the remaining chocolate chips.
Bake for 25–30 minutes, until the edges are set but the center still looks slightly soft.
Let cool completely before slicing.
Store the cooled brownies in an airtight container at room temperature for up to 2 days. In the refrigerator, they will keep for about 4–5 days. You can also freeze the brownies for up to 2–3 months.