Preheat the oven to 400ºF. Cut the zucchini into a very small dice, just slightly larger than the pieces of corn. Combine the diced zucchini, corn, olive oil, taco seasoning, and garlic powder in a bowl. Stir until everything is well combined and coated in oil and seasonings.
Cover a baking sheet in foil and spread the zucchini and corn mixture evenly over the surface. Roast in the preheated oven for 25 minutes, or until the vegetables look slightly shriveled. Meanwhile, rinse the black beans and let them drain well.
After the vegetables have roasted, combine them with the well drained black beans. Season the mixture with extra salt, if needed (I used about 1/4 tsp). Cut the avocado into 12 slices.
Lightly toast the corn tortillas in a dry skillet, then top with a small scoop of the zucchini corn mixture, a slice of avocado, a few sprigs of cilantro, and a pinch of shredded monterrey jack cheese.