Preheat your oven to 350 degrees F. Line two baking sheets with parchment paper and set aside.

Grate the zucchini on the large holes of a box grater. Wrap it in a clean kitchen towel and squeeze hard until most of the liquid is gone. The zucchini should feel close to dry and the towel will be very damp. Skipping this step leads to dough that is too wet and cookies that do not bake through properly.

In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking soda, baking powder, and salt until evenly combined. If your cocoa has any lumps, sift it first so it blends smoothly.

In a large bowl, whisk together the melted butter, granulated sugar, and brown sugar until the mixture looks smooth and slightly thickened, about 1 minute. Add both eggs and the vanilla and whisk vigorously for another 30 seconds until glossy.

Stir in the squeezed zucchini with a rubber spatula. Add the dry ingredients and fold until just combined and no dry streaks remain. The dough will be thick and dark.

Fold in the chocolate chips, distributing them evenly throughout the dough.

Scoop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart. The dough is scoopable but slightly sticky, which is normal.

Bake one sheet at a time on the center rack for 10 to 12 minutes. The edges should look set and the tops should appear just barely dry, but the centers will still look underdone and soft. That is correct. Pull them from the oven at that point.

Let the cookies cool on the pan for 5 full minutes before moving them to a wire rack. They need this time to firm up or they will fall apart. Once fully cooled, the centers will be dense, fudgy, and soft in the best possible way.