Heat oil in a large skillet over medium-high heat. (You can skip this stove-top step if you prefer or are in a pinch. Just add chicken directly to slow cooker. The chicken will not have that crispy coating) Cook chicken about 2-3 minutes on each side, until lightly browned. Transfer chicken into the slow cooker and pour sauce over top.
About 30 minutes before serving, whisk together the cornstarch and water in a small bowl and stir into the slow cooker. Toss in the dried red chili peppers, red bell peppers, zucchini, and cashews, stirring to combine. Cover and cook on HIGH for another 20-30 minutes or until the vegetables are tender and the sauce has thickened up. (if your slow cooker is not hot enough to thicken the sauce - pour sauce into a pot and heat on the stovetop on high to thicken the sauce or you can just skip the cornstarch slurry instead)
Return inner pot back to the Instant Pot. Press the SAUTE button and add additional oil as needed. Toss in the zucchini, bell peppers, and dried red chili peppers. Cook for 2-3 minutes, until tender. Combine the cornstarch with water to make a slurry and stir into the Instant Pot. Allow the sauce to bubble and thicken up. Return chicken back to the pot along with the cashews and cook for another 1-2 minutes until everything is heated through.