Heat oven to 425°F / 218°C.
Slice zucchini in half lengthwise and arrange in a single layer in a large baking dish (or sheet pan), cut-side up. Sprinkle the zucchini with some salt and transfer to oven. Roast until softened slightly, about 10 minutes.
While zucchini roasts, in a large mixing bowl, combine black beans, corn, rice, salt, paprika, cumin, chili powder, garlic powder, black pepper, and 1/2 cup cheese.
Remove zucchini from oven and let cool slightly. Working carefully, use a spoon to scrape out the center of the zucchini, leaving the peels intact. Add any zucchini that you scrape out to the bowl with the rice mixture and stir everything to combine well.
Season zucchini shells with some salt.
Spoon the rice mixture into the zucchini shells, pressing it down gently, and mounding it over the tops. (You can make this more casserole-style and just spread the rice mixture out over top of all the zucchini or fill each zucchini separately, pressing the rice mixture down into the zucchini.)
Top the zucchini with 1 cup cheese.
Return zucchini to oven and continue cooking until filling is warmed through and cheese is melted, 10 to 15 minutes more.
Serve the zucchini with sour cream, salsa, and chopped cilantro. Add tortilla chips for crumbling over top or serving on the side. Enjoy!