In a pressure cooker on medium high heat, add oil, cumin seeds and the diced onions.
Saute until the onions become translucent, then add the ginger-garlic paste. Saute for 30 seconds.
Add the diced tomatoes along with the spices - salt, turmeric powder and red chili powder.
Cook until the tomatoes break down and become mushy.
Then add the chopped zucchini and saute for 1-2 minutes.
Add the 1/2 cup water, close the pressure cooker with its lid and pressure cook for 10 minutes (time is noted when the pressure cooker starts whistling).
Once 10 minutes are done, turn off the heat and safely open the pressure cooker once its pressure has been released.
At this point you will notice the curry is very watery (zucchini releases its own water). Turn on the heat to high so that the water evaporates.
At the same time, using the back of a large spoon or a potato masher, start mashing the zucchini.
Keep cooking until the curry has reached your desired consistency.
Garnish with chopped green chillies or chopped cilantro. Serve hot with roti/naan/rice.