Place onion, broth, water, farro, diced tomatoes, salt, oregano, basil and garlic in Instant pot
Seal IP and make sure the venting knob is in the sealed position. Press pressure cook button, make sure it is on high and normal (default factory settings) and set the timer for 20 minutes
Cut the zucchini in ½ inch wheels and then in quarters. Also cut the corn kernals off the cob and set aside.
Once the timer beeps to indicate it's done, wait 5 minutes before you do a quick release - don an oven mitt and nudge the knob to the venting position
Once the pressure has been released, open cover and pour in the zucchini and corn in with the soup. Give it a quick stir then seal the IP. Make sure the venting knob is set to sealed and press the pressure cook button and set the timer for 3 minutes. The IP shouldn't take as long to come back to pressure
Once the timer beeps, wait 5 minutes before doing another quick release. Open cover and transfer soup into a serving dish or pan.