Gather all ingredients and measure them out for efficient cooking. Cut the chicken breasts into 1-inch pieces and place them in a bowl. In a small dish, combine the salt, black pepper, lemon zest, garlic powder (3/4 tsp), onion powder, and Italian seasoning (1/2 tsp). Toss the chicken pieces with this seasoning mixture until evenly coated, allowing the flavors to begin penetrating the meat. Slice the zucchini and yellow squash into 1/4-inch half-moons and set aside.

While the pasta water comes to a boil, start cooking the chicken. Heat 2.5 tablespoons of olive oil in a large skillet over medium-high heat until shimmering. Add the seasoned chicken pieces in a single layer and cook for 3-5 minutes per side until golden brown and cooked through, working in batches if needed to avoid overcrowding. Transfer the cooked chicken to a plate. Meanwhile, cook the pasta according to package directions until al dente, then drain and set aside.

In the same skillet, add the 1 tablespoon of olive oil and sauté the sliced zucchini and yellow squash for 2 minutes until they begin to soften. Add the freshly minced garlic cloves along with the garlic powder (1/2 tsp), Italian seasoning (1/2 tsp), and red pepper flakes, cooking for 30 seconds until fragrant. I like to add the garlic at this point rather than earlier so it doesn't brown and become bitter—the quick sauté releases its fresh flavor perfectly. Immediately add the butter and lemon juice, stirring constantly until the butter melts completely and creates a bright, silky sauce.

Add the cooked pasta from Step 2 to the skillet with the sauce and vegetables, tossing gently to coat everything evenly. Chop the reserved cooked chicken into bite-sized pieces and return it to the skillet. Stir in the parmesan cheese until fully incorporated and the dish is creamy and cohesive. Taste and adjust seasoning with salt and pepper as needed. I prefer to add the parmesan at the very end so it doesn't clump or become grainy from prolonged heat.

Divide the lemon chicken pasta among serving bowls or plates. Garnish generously with fresh chopped parsley and a small handful of additional parmesan cheese for brightness and richness. Serve immediately while the pasta is warm and the sauce is creamy.