Heat oil in a pan. Now add mustard seeds once they stop splattering add onion, green chili and sauté until onion turns translucent (golden brown).
Now add zucchini pieces, turmeric powder, salt, chili powder. Place a lid and cook for 5 minutes or until the zucchini is cooked. NOTE: stir time to time to avoid burning. sprinkle water if needed when you cook the zucchini