Bring a pot of salted water to a boil and cook the spaghetti according to package directions until al dente, reserving 2 tablespoons of pasta water before draining.
While pasta cooks, dice the chicken breast into bite-sized pieces and finely chop the pancetta.
In a medium skillet over medium heat, cook the pancetta until the fat renders and it becomes crispy.
Add the diced chicken to the skillet with the pancetta and sauté until cooked through and golden brown, approximately 5-7 minutes.
Stir in the minced garlic and cook for 30 seconds until fragrant, then add the zucchini noodles to the pan for 1 minute just to soften.
In a small bowl, whisk the egg, parmesan cheese, sea salt, and black pepper until well combined.
Turn off the heat entirely. Add the cooked spaghetti to the skillet with the chicken and zucchini.
Quickly pour the egg mixture and reserved pasta water over the warm pasta, tossing constantly for 1 minute to create a creamy sauce without scrambling the eggs.
Serve immediately while the sauce is silky and warm.