Preheat oven to 350 degrees F. Line a muffin pan with paper liners.
Whisk together flour, orange zest, baking powder, cinnamon, baking soda, and salt in medium mixing bowl; set aside.
Whisk together oil and sugar together in a large mixing bowl. Whisk in ricotta, egg, vanilla, then milk until well combined.
Mix dry ingredients into the oil and sugar mixture until just combined. Reserve about 2 tablespoons each of chocolate chips and pistachios for tops of muffins, then mix the rest into the muffin batter.
Scoop batter evenly into paper-lined pan filling cups about ⅔ full. Sprinkle reserved chocolate chips and pistachios on top of batter.
Bake muffins at 350 degrees F for about 20-25 minutes or until golden brown around the edges. Cool slightly, then remove from pan and cool on a wire rack. Dust with powdered sugar.
