In a small bowl, combine the chili powder, cumin and 1 teaspoon salt. Dust the turkey cutlets on both sides with the spice mixture.
In a large skillet, heat 1 tablespoon oil over medium heat. Add the onion and garlic and cook until softened, about 5 minutes. Add the zucchini and the remaining 1/2 teaspoon salt and cook, stirring occasionally, for 4 minutes. Stir in the corn and tomatoes and simmer until the zucchini is tender, about 4 minutes. Cover to keep warm.
In another large skillet, heat the remaining 2 tablespoons oil over medium-low heat. Working in batches, add the turkey cutlets and fry until just cooked through, 2 to 3 minutes on each side. Transfer to a paper-towel-lined plate to drain. Serve with the Mexican squash.