Press on SAUTE on your Instant Pot, when a HOT message appears add the vegetable oil, along with sesame oil. Sear the meat in the Instant Pot until it's brown (but not necessarily cooked through as it will be pressure-cooked later), and season it with salt and pepper.
Add minced ginger and garlic to the pot, and cook for a couple of minutes. Press on CANCEL on the Instant Pot. Then add the onions and mushrooms, soy sauce, water, and vinegar, and give everything a quick mix. If anything is stick to the bottom of the pot, deglaze/scrape it off with a wooden spoon.
Secure the lid and set the vent to SEALING. Select the PRESSURE COOK/MANUAL setting and set the cooking time for 4 minutes at high pressure.
The Instant Pot will take around 10 minutes to come to pressure and start cooking. When the cooking program ends, quickly release the steam and carefully open the pot.
Now you will thicken the sauce by adding 1 tablespoon of cornstarch mixed with 1 tablespoon of water. Press on SAUTE and add the corn starch slurry to the sauce once it's boiling. Mix with a wooden spoon until the sauce has thickened. Press on CANCEL, and add in the sliced zucchini. Cover with the lid and let the zucchini "steam" for 5 minutes".
Serve over cooked white rice, or brown rice and garnish with toasted sesame seeds and sliced green onion.