Preheat oven to 350º.In a large skillet over medium heat, heat oil.Add onion and season with salt.Cook until soft, 5 minutes, then add garlic, cumin and chili powder and stir until combined.Add shredded chicken and 1 cup enchilada sauce and stir until saucy.On a cutting board, use a Y-shaped or wide vegetable peeler to make thin slices of zucchini.Lay out three, slightly overlapping, and place a spoonful of chicken mixture on top.Roll up and transfer to a baking dish.Repeat with remaining zucchini and chicken mixture.Spoon remaining 1/3 cup enchilada sauce over zucchini enchiladas and sprinkle with both cheeses.Bake until melty, 20 minutes.Garnish with sour cream and cilantro and serve.