Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. Scoop out the inside flesh of the zucchini halves, leaving about 1/4-inch rim to create the boats. Reserve the zucchini flesh for later. Place each zucchini, cut side up, onto the prepared baking sheet and rub with 1 tablespoon avocado oil. Season with sea salt, then bake until they just begin to soften, about 12-15 minutes.
Meanwhile, heat the remaining avocado oil in a large skillet over medium-high heat. Add onion and sauté for 3 minutes. Stir in garlic and cook until fragrant, 1 minute. Add in ground turkey or beef and cook, breaking up the meat with a wooden spoon, until just cooked through. Sprinkle meat with the chili powder and cumin, then stir in tomatoes, beans, corn, lime juice, and remaining zucchini flesh. Cook on low heat for 5-7 minutes. Season to taste with salt and pepper.
Carefully spoon the taco mixture into your zucchini boats and top with cheese. Return to the oven and bake until cheese is melty and zucchinis are tender and heated through, about 10 minutes. Top with chopped fresh herbs before serving.