Preheat oven to 400ºF. Lightly coat 9 X 13 baking dish with nonstick cooking spray.
Cut each zucchini in half horizontally. Trim off the ends. Carefully scoop out the center of zucchini. Reserve zucchini pulp for later and leaving 1/2" of zucchini skin. Lay zucchini in prepared baking dish.
Take zucchini pulp and squeeze out excess water with a cheesecloth or paper towel.
In a large frying pan, heat olive oil over medium-high heat. Add ground turkey and onion. Cook turkey until no longer pink and onions are fragrant, about 8-10 minutes.
Add taco seasoning, kosher salt, reserved zucchini pulp, and diced tomatoes with green chiles. Stir until thickened and flavors have blended, about 5 minutes.
Drain and rinse black beans. Add black beans and corn to mixture. Cook another 2-3 minutes. Stir in cilantro until well combined.
Add turkey mixture to each zucchini. Top with sharp cheddar cheese. Cover with aluminum foil. Place into oven and bake at 400ºF for 25-35 minutes.
Remove from oven. Garnish with more cilantro and green onions. Serve with avocado, fresh salsa and sour cream.