In a bowl, combine the chickpea flour and 3/4 cup water. Whisk to get a smooth consistency. Whisk in another 1/2 to 3/4 cup water to make a thin lump-free batter. (If using besan, you will need less water to get the same consistency).
Add the salt, turmeric, cayenne, carom seeds, onion, chile, cilantro, and 1 teaspoon of oil, and mix well. Add zucchini if using. Let the batter sit for 5 minutes.
Heat a skillet over medium heat. When the skillet is hot, drizzle a few drops of oil on the skillet. Spread the oil using a paper towel. Pour a ladle full (1/4 to 1/3 cup) of the batter onto the skillet. Spread the batter by moving the skillet to make a 6 to 8-inch pancake. Drizzle a few drops of oil on the edges of the pancake.
Cook until the edges start to leave the pan and the bottom is golden brown, 4 to 6 minutes. Flip and cook for 2 to 4 minutes. Continue to make the rest of the pancakes. Serve hot with ketchup, chutneys or sriracha. Chilla can also be stuffed with roasted veggies or potatoes.