Heat the oil on medium flame. Sauté the onion and garlic several minutes. With the Instant Pot, do this on the Sauté function. (see note) Add the zucchini, chile, celery, if using, and the parsley or basil. Pour in the vegetable broth—it will barely, or not even, cover the vegetables in the cookpot.
With the Instant Pot, manually set the time to 6 minutes. Quick release the pressure using the top vent.
For stovetop pressure cooker—bring to pressure and cook for 6 minutes. Quick-release the pressure under cold running water.
For regular stovetop cooking without a pressure cooker or Instant Pot, cover and simmer the vegetables and broth until the zucchini is very soft, about 20 minutes.
Puree using an immersion blender or puree in batches in a blender jar. (see note) Season to taste with salt.
Add the cooked rice, and heat until the rice is hot.
Serve with cheese, if desired. Or garnish with pumpkin seeds and/or slices of avocado.