Stir all the ingredients to together in a bowl, then pour it over the meat. Toss the chicken pieces until they are well coated in the marinade, then cover then refrigerate for 20 minutes up to overnight.
Whisk all the ingredients together, except the cornstarch and water, then set aside.
Heat up 1 tablespoon of oil in a large wok over medium-high heat, add the dried red chili peppers and cook until they start to turn black, roughly 15 to 30 seconds. Remove from the wok and place in a bowl. The peanuts are roasted in oil for 3 minutes over medium heat while constantly stirring then they are removed from the heat and continue to roast for another minute using residual heat. Set aside to cool. Heat up 2 tablespoons of oil. Add the meat (discard the marinade to reduce moisture) and quickly spread it out so it is in one layer. Allow it to cook for 2 minutes, then flip and cook the other side. The chicken should be 80% cooked. Remove from the wok and place in a bowl.
Heat up 2 tablespoons of oil, then add the red bell pepper and the zucchini. Stir fry for 1 ½ to 2 minutes over medium-high heat, stirring constantly. Remove from the wok and place in a bowl.
Add the garlic and ginger and stir constantly until fragrant, roughly 15 seconds, then add the sambal oelek and cook for 15 seconds. Remove from the wok and place in a bowl with the red chilies.
Whisk the cornstarch and water to form a slurry, then mix it into the sauce. Pour it into the wok and stir until it thickens, roughly a minute.
Add the chicken to the wok and stir until each piece is well coated in the sauce. Add the veggies and the dried whole red chilies, then mix in the sliced green onion and the peanuts. Stir and cook for 2 minutes, or until the meat is fully cooked (no longer pink in the center).
Remove from the heat and stir in 1 teaspoon of red pepper flakes.
Serve wth your favorite Panda Express side dish: super greens, steamed rice, fried rice, or chow mein. Garnish the Kung Pao chicken with sesame seeds and green onion, if desired.