Remember the reserved soy/honey/sesame oil sauce we set aside? Pour in just half of that sauce and toss well. Remove the vegetables to the large serving bowl with the egg. Give the pan a good wipe if needed, return to medium-high heat. When hot, swirl in cooking oil.
Add in the zucchini noodles and stir fry until the skin of zucchini is vivid green, and the zucchini begins to turn transluscent. The zucchini should still hold some of its curly shape. Take care not to overcook the zucchini. Pour in the last of the soy/honey/sesame oil sauce. Toss very well and let the zucchini absorb some of the sauce. Remove the zucchini noodles to a large bowl. Give the pan a good wipe, return to HIGH heat. When hot, swirl in cooking oil. Add in the beef and onion to the pan, use your spatula to spread out the ingredients all over the pan. Let cook, undisturbed for 15-30 seconds, until the edges of the beef turn brown, but is still red in the middle. Toss and flip the beef and onions, stir fry until cooked to your liking. Now lets add everything back into the pan. Add in the egg, vegetables, zucchini noodles. Toss well and give it a taste. Season with additional soy sauce, if needed. Sprinkle with sesame seeds and serve.