Bring a large pot of salted water to a boil and cook the whole wheat penne according to package directions until al dente, reserving 2 tablespoons of pasta water before draining.
While the pasta cooks, pat the chicken breast dry and season both sides evenly with sea salt, black pepper, and dried oregano.
Heat the extra virgin olive oil in a large skillet over medium-high heat and sear the chicken until a golden-brown crust forms and it is cooked through, about 5-6 minutes per side.
Remove the chicken from the pan to rest for 3 minutes, then slice into thin strips.
In the same skillet, add the sliced zucchini and minced garlic, sautéing for 2-3 minutes until the zucchini is tender-crisp and fragrant.
Add the cooked pasta, baby spinach, lemon juice, lemon zest, and reserved pasta water to the skillet, tossing until the spinach is just wilted.
Return the sliced chicken to the pan, garnish with fresh chopped parsley, and serve immediately.