Preheat oven to 375° and spray a 9x13 baking pan with non-stick cooking spray; set aside.
Bring a large pot of water to a roiling boil. Cut the zucchini in half length wise and scoop out flesh. Make sure to leave about 1/4" thick. Take extra zucchini and chop into small pieces. Set aside. Place zucchini in the pot of boiling water and cook for 1 minute. Remove from water and set on a paper towel.
In a large pan, heat oil and add onions. After 2 minutes, add garlic and bell pepper. Cook for about 3 minutes, until onions become translucent and bell pepper soften. Add zucchini, cilantro, salt, pepper, cumin, oregano, and chili powder. Cook for 5 minutes. Stir together chicken and taco seasoning in a bowl then add to pan. Add in corn and black beans, mix until all ingredients are incorporated.
Place 1/4 cup enchilada sauce on the bottom of prepared baking dish. Place zucchini halves cut side up. Using a spoon, fill each hollowed zucchini with chicken mixture. Top enchilada boats with enchilada sauce and cheddar cheese.
Cover with foil and bake for 30 minutes or until cheese in melted and zucchini is cooked through. Let sit 5 minutes, then top with cilantro and additional cheese, if desired. Garnish with sour cream. Serve & enjoy!