Heat the oil in a large skillet until shimmering. Add the sweet potato, onion, and mushroom, and toss to coat. Cook for several minutes, stirring, until onions start to go clear.
Add the zucchini and season the vegetables to taste with salt and pepper. Continue cooking until the zucchini and sweet potatoes are tender. Adjust seasonings and serve.
Hash can be made in advance and stored in an airtight container in the refrigerator for up to 3 days. Reheat in a skillet or in the microwave.
Notes
Nutritional values are approximate and are based on ¼ of the recipe. Refrigerate leftovers promptly and use within 4 days.