Begin by selecting SAUTE on your Instant Pot. Once the HOT message appears, add vegetable oil and sesame oil. Sear the meat in the Instant Pot until it's browned (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 CANCEL on the Instant Pot. Then add the onions and mushrooms, soy sauce, water, and vinegar, and give everything a quick mix. If anything sticks to the bottom of the pot, deglaze/scrape it off with a wooden spoon.
Secure the lid and set the vent to SEALING. Choose the PRESSURE COOK/MANUAL setting and set the cooking time for 4 minutes at high pressure.
The Instant Pot will take approximately 10 minutes to come to pressure and begin cooking. When the cooking program finishes, promptly release the steam and cautiously open the pot.
Now, thicken the sauce by adding 1 tablespoon of cornstarch mixed with 1 tablespoon of water. Press SAUTE and add the cornstarch slurry to the sauce once it's boiling. Mix with a wooden spoon until the sauce has thickened. Press CANCEL, and add in the sliced zucchini. Cover with the lid and let the zucchini "steam" for 5 minutes.
Serve over cooked white or brown rice and garnish with toasted sesame seeds and sliced green onion.