Heat 2 teaspoons avocado oil in a large skillet over medium-high heat. Swirl to coat the bottom.
Cook diced sweet potatoes for 4-5 minutes, stirring occasionally, until they start to soften.
Add zucchini, red bell pepper, onion, and minced garlic. Cook for another 3-4 minutes until vegetables are tender-crisp.
Push vegetables to one side of the skillet. Add ground beef to the empty side and cook for 7-9 minutes, breaking it into smaller pieces as it browns.
Once the beef is fully cooked, drain any excess grease.
Lower the heat to medium-low. Add black beans, fire-roasted tomatoes (with juice), frozen corn, and taco seasoning. Stir to combine.
Top with shredded cheese, cover with a lid, and remove from heat. Let the cheese melt for about 2 minutes.
Garnish with fresh cilantro or green onions, then serve warm.