Preheat oven to 400°F. Cut zucchini in half lengthwise and scoop out flesh, leaving 1/4 inch thick. Chop the scooped flesh and set aside.

In a large saute pan, heat 1 tablespoon olive oil and add chopped zucchini flesh, green onions, garlic, and bell pepper. Cook on medium-low for 4 minutes, then add cumin, oregano, chili powder, water, and tomato paste. Mix in shredded chicken and cook for 3 more minutes.

Place 1/4 cup of enchilada sauce at the bottom of a baking dish. Fill each zucchini half with chicken mixture, pressing firmly, then top with 2 tablespoons of enchilada sauce and 1/2 cup cheese. Cover with foil and bake for 35 minutes until cheese is melted and zucchini is tender.

Garnish with chopped cilantro and scallions, serve with Greek yogurt or sour cream if desired.