Preheat oven to 400º F. Combine zucchini, mushrooms, onion and cherry tomatoes on a large baking sheet.
Mix together olive oil, garlic powder, salt and cumin in a small bowl. Drizzle over veggies. Toss with your hands until veggies are covered. Push veggies to one side and place frozen burgers on the baking sheet.
Bake in preheated oven for about 20 minutes, turning veggies and patties throughout cooking.
While your vegetables and patties bake, mash avocados in a medium sized bowl. Add Greek yogurt, lime juice and salt.
When veggies are tender and burger patties are golden brown, pull from oven. Carefully slice up burgers into chunks and place on tortillas. Add roasted veggies. Sprinkle with feta cheese and cilantro. Top with avocado crema sauce. Devour and enjoy!