Cut the zucchini into large chunks and keep it aside. If you wish you can peel the zucchini, I kept the skin on.
Heat oil in a large pan on medium high heat. When hot add the onions and sauté for 5 mins until soft and turns golden.
Then add the ginger-garlic paste and sauté for 1-2 minutes.
Add in the chilli powder, coriander powder, cumin powder, turmeric powder and salt Sauté for few seconds.
Then add in the chopped tomato and sauté until soft and mushy.
Then add 3/4 cup of water and cover and cook the masala on medium-low heat for 7-8 minutes, stirring intermittently. Cook until you see the oil separate from the masala.
Then add the prawns and mix. cook for a minute or 2 until it is no longer raw.
Toss in the zucchini in the masala and mix everything well.
Cover and cook for 12 to 15 minutes or until the zucchini is soft and cooked through.
Finally add the chopped coriander and sliced green chillies and cook for 2 minutes. Then take it off the heat.
Serve it hot with rice or roti.