Trim chicken breasts and cut into 8 equal-sized pieces. Season on both sides with salt, pepper and garlic powder.
In a large skillet over medium-high heat, add olive oil and heat until shimmering. Place chicken in skillet and cook 3–4 minutes per side or until cooked through. Remove chicken to a serving platter and cover with foil to keep warm.
Wipe out skillet and reduce heat to medium. Add olive oil and heat until shimmering. Add spiralized zucchini and season with salt and pepper. Cook for 1–2 minutes, until zoodles are al dente. Transfer to a large mixing bowl while you make the sauce.
Wipe out skillet. Melt the butter and then add flour, stirring to combine. Cook flour, whisking constantly for approximately 1 minute until it just begins to turn light brown. Whisk in milk and allow the mixture to come to a bubble.
Stir in oregano, garlic powder and lemon zest then reduce heat to low and simmer 5–6 minutes, stirring occasionally until slightly thickened. Add feta crumbles, stir until cheese is mostly melted then remove from heat.
Season sauce to taste with salt and pepper and adjust consistency of sauce with a bit of extra milk if necessary.
Pour sauce over zoodles, reserving a bit of sauce for the chicken. Stir to combine then portion out the zoodles on plates and top with sliced chicken. Garnish with some sauce, more feta cheese crumbles, green onions and a few red chili flakes if you like heat. Enjoy!