In a small bowl, mix together the sauce ingredients (hoisin, Sriracha, sesame oil, soy sauce, ginger, water) and whisk until well combined. Set aside.

In a large pot of boiling water, blanch the udon noodles for 1 to 2 minutes (no need to break the noodles apart as they will separate as they blanch). Note: if using dry noodles cook according to package instructions, until al dente. Drain well and immediately rinse with cold water. Set aside.

Heat the oil in the wok on medium-high to high heat. Add the carrot and cabbage, and stir-fry for 1 minute, then add the zucchini. Stir-fry for a minute or so, tossing constantly until all the vegetables are lightly seared and starting to soften.

Add the udon noodles to the wok. Stir-fry for one minute, then pour over the sauce. Stir-fry for another minute, tossing constantly until everything is thoroughly coated in the sauce is heated through. Add half the green onion, stir to combine.

Serve into bowl, topped with the remaining green onions a sprinkle of sesame seeds. If desired, add an extra drizzle of Sriracha chili sauce and enjoy!