Heat 2 tsp of oil in a pan, fry the channa dal and urad dal until they turn brownish. Keep aside.
In the same oil, fry ginger, garlic, and tamarind until they turn brown.
Fry the red chillies and green chillies one by one in the same pan.
Cut the zucchini into small pieces and fry them. (zucchini cooks very easily) Keep aside to cool.
In a food processor, put all the fried ingredients, add salt and grind. (There is no need to add water as zucchini will release sufficient water. Grind to a smooth paste or coarsely according to your preference.)
Heat oil in a pan, splutter mustard seeds and urad dal. Add the curry leaves.
Pour the ground mixture into this, stir and cook for a while.