In a medium bowl, whisk together broth, soy sauce, brown sugar, garlic, and red pepper flakes. Reserve until ready to use.
In a large non-stick skillet, heat 1 tablespoon oil over medium-high heat. Add chicken and sauté 3-4 minutes or until browned. Add broth mixture and bring to a boil. Reduce heat to medium-low and cook until chicken is cooked through and internal temperature reaches 165℉.
Mix cornstarch and 1 ½ tablespoons water. Add slurry to chicken, along with pineapple and cashews. Cook until thickened, about 10 minutes.
In a large skillet, heat 1 tablespoon oil over medium heat. Add zucchini noodles and sauté 3-4 minutes. Transfer to a large plate.
To the same pan, add broccoli florets and ¼ cup water, cover, and let steam 4-5 minutes or until just tender. Transfer to a separate plate.
To serve, divide zucchini noodles among 4 bowls. Top with chicken mixture and steamed broccoli. Garnish with extra chopped pineapple and serve immediately.