Preheat the oven to 350°F (180°C). Grease a 9×5 (or 8×4) inch loaf pan. PRO TIP: when greasing pans for quick bread is best to use shortening instead of butter, since butter has water in it can cause sticking. Also, just brush the shortening over the bottom and half up to the sides of the pan; this will help the bread its height as it rises.
Whisk the flour, baking powder, baking soda, salt, and cinnamon, together in a large bowl until well combined. Set aside.
In a medium bowl, whisk the oil, brown sugar, granulated sugar, yogurt, milk, vanilla, and zucchini together until combined.
Pour the wet ingredients into the dry ingredients. Gently whisk until just combined; please do not overmix. Foil in the chocolate chips, if using. The batter will be a bit thick, that is okay.
Spread the batter into the prepared loaf pan. Sprinkle with more chocolate chip, if desired.
Bake for 50 – 55 minutes, or until a toothpick inserted in the center comes out mostly clean (no raw batter, a few moist crumbs are okay). NOTE: if the bread is browning too fast, loosely cover the bread with aluminum foil halfway through to prevent heavy browning on top.
Allow cooling completely before slicing.