Whisk all of the ingredients for the stir fry sauce together and set aside.
Clean, dry, and chop the vegetables.
Preheat a large cooking pan or a wok over medium-high heat.
Once the pan is preheated, spread oil in it and add the veggies. Toss the veggies and let them sear for 30-40 seconds or so, undisturbed, to start to get a golden sear.
Once veggies start to brown, stir them again, every 20-30 seconds, until almost reached your desired doneness. (Since you're cooking on higher heat, frequent stirring prevents burning while you sauté the veggies evenly all around.)
When veggies are almost as done as you like them, give the sauce a quick whisk and pour it over the veggies. Stir and cook until the sauce thickens, which should take only a minute or so.
Top the veggies off with some green onion and sesame seed and take off heat. Serve them right away.
Notes
Thai roasted red chili paste substitute: it's hard to substitute it exactly but you can use a dash of Sriracha or chop up a Thai chili pepper or a serrano but be careful, it will be much spicier so start with less. Thai chili paste is mild in heat so be mindful of chili peppers.
Vegetables options: you can always alter the vegetable used in this stir fry as you wish. You can keep it just zucchini and onion, just increase the amount of zucchini. Or add more veggies like carrots, bell peppers, baby corn, or snap peas.
Store in an air-tight food storage container, in the refrigerator, for 3-4 days.
Reheat quickly in a preheated cooking pan, over medium heat, until just heated through.