Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone liners.
Whisk together the flour, baking powder, salt, and cinnamon. Stir in the oats. Set aside.
Using an electric mixer on medium speed, beat the butter, brown sugar, and sugar until light and fluffy. Add the egg, and mix well. Mix in the vanilla.
Reduce mixer speed to low. Gradually add the flour mixture, mixing just until there are a few streaks of flour remaining.
Stir in the zucchini, chocolate chips, and nuts.
Drop the dough by 2-tablespoon portions onto the prepared pans, leaving about 2 inches between cookies.
Bake, one pan at a time, 12 to 16 minutes, or until the cookies are golden brown.
Cool the cookies on the pan on a wire rack for 5 minutes. Then transfer the cookies from the pan to a wire rack to cool completely.
Notes
*Don't worry much about trying to remove the water from the zucchini. I usually just pat the shredded zucchini with a paper towel to remove the excess.