Soak beans with a good amount of water overnight. Once soaked, drain and rinse the beans. Place the beans in a large pot and cover with fresh water. Add 1 tsp. salt to the cooking water. Place on the stovetop and bring to a boil, then reduce to a simmer. Simmer for 1 hour, or until you reach desired tenderness. Stir the beans a few time so they don’t stick to the bottom. Drain out most of the water. You should leave about 1/2 inch of water at the bottom. Add 1 Tbsp. olive oil, minced garlic, 1/4 cumin, a pinch of salt and pepper. Cook for a couple minutes, stirring constantly, then remove from heat, cover and set aside.
Using a mandolin or sharp chef’s knife slice radishes into paper thin rounds and cabbage into thin strips. Transfer to a medium bowl and mix in the scallions, 1 Tbsp. olive oil, lime juice and 1/4 tsp. of salt. Massage and squeeze the cabbage with your hands to help it release its liquid and begin wilting. Set aside.
Slice zucchini into thin rounds. Heat 2 Tbsp. olive oil in a large skillet over medium-high heat. Add the zucchini and cook, stirring only occasionally, until golden brown, about 10 minutes.
Add corn and cook for couple more minutes.Set a large pan over medium-low heat. Arrange 2-3 tortillas in a single layer. Flip them after 30 seconds or so. As they come off the stove, wrap them in a clean tea towel. Repeat with a second batch. Fill each taco with black beans and zucchini. Top with cabbage slaw and cilantro leaves.