Preheat oven to 350°F (177°C). Grease a 9×5-inch loaf pan with nonstick spray. Set aside.

In a large bowl, whisk the flour, baking powder, baking soda, salt, and cinnamon together. Set aside.

In a medium bowl, whisk the oil, peanut butter, brown sugar, honey, eggs, milk, and vanilla together until combined. Pour the wet ingredients into the dry ingredients. Gently stir or whisk until *just* combined; do not overmix. With a silicone spatula, fold in the zucchini and chocolate chips. Batter is slightly thick.

Spread the batter evenly into the prepared loaf pan. Bake for 55–70 minutes, making sure to loosely cover the bread with aluminum foil halfway through to prevent the top from over-browning. The bread is done when a toothpick inserted in the center comes out clean with only a few small moist crumbs.

Remove the bread from the oven and set on a wire rack. Cool in the pan for 1 hour before removing from the pan. You can slice the bread at this point, but it will still be warm in the center and may not slice neatly. For neat slices, cool the bread completely on a wire rack before slicing.

Cover and store bread at room temperature for 5 days or in the refrigerator for up to 1 week. Bread tastes best on day 2 after the flavors have settled together.