Cook pasta in a large pot of generously salted water according to to package directions. Drain reserving 1 cup of pasta water. Set asside.
Melt butter in a large skillet over medium heat. Add leeks and cook. Stirring often, until very soft, about 4 minutes. Add half and half, and cheese. Cook stirring constantly, until melted and thickened, 3-4 minutes. Stir in vegetables, salt and .25 teaspoon of pepper. Cook, stirring often until vegetables are cooked through and tender.
Add pasta and .5 cup of pasta water to skillet. Stirring gently until sauce thickens, about 1 minutes. Add remaining .5 cup of pasta water if needed to loosen sauce. Top with chives and lemon zest. add remaining .25 teaspoon of pepper.