Preheat the oven to 350ºF. Grease a 9x5 loaf pan well, or line with parchment.

In a large bowl, combine the sugar, oil, eggs, and vanilla. Whisk to combine.

In another bowl, whisk together the flour, cocoa powder, baking soda, and salt. Add this to the sugar mixture and stir together until it is about halfway mixed together. The batter will be very thick.

Add the zucchini and continue to mix until mostly combined. Reserve about 2 tablespoons of the chocolate chips, and add the remaining to the batter. Continue to stir just until everything is combined. (The batter will still be quite thick - but you should be able to stir everything together.)

Transfer the batter to the prepared loaf pan. Spread the batter to an even layer.

Bake until a tester inserted in the middle comes out mostly clean, about 1 hour. (When testing, it can be tricky if you hit a chocolate chip, so you may want to test in a few different areas.)

Let the bread cool before removing from the pans to slice and serve.