Trim the stems ends off from the zucchini and cut them in half, lengthwise. Use a spoon to carefully scoop the flesh out of each zucchini half. Chop the flesh into small pieces, then set aside to add to the meat mixture.
Heat the olive oil in a large frying pan over medium-high heat. Add the onion and saute for 4-5 minutes. Next add the lean ground beef and ½ tsp. salt and cook until browned, breaking it into small pieces. Drain off any fat if needed.
Add in the minced garlic and zucchini pieces. Saute the ingredients for another 5 minutes.
Add the drained black beans and corn, enchilada sauce, remaining salt, and cumin. Stir well and season to taste with more salt if needed. Set aside.
Place the zucchini halves onto a baking sheet. Divide the ground beef mixture evenly between the shells.
Sprinkle the tops with grated cheese and bake at 400 degrees F for 30 minutes, until the cheese is slightly browned and melted. Top with fresh minced cilantro and serve.