Take a shallow 3quart baking dish ready.
Heat oil in a large nonstick skillet on a medium-high heat.
Add zucchini and saute 5 to 6 minutes until it just starts to brown.
Remove it to a small bowl.
Add beef, onions, and garlic to skillet. Cook, stirring to break up beef, until browned.
Add tomatoes, seasoning, sugar and salt. Bring to a simmer and cook for about 6 minutes.
Meanwhile, whisk together milk and flour in a 2-quart saucepan until smooth. Bring to a boil over medium heat, whisking often. Boil for about 3 to 4 minutes until it slightly thickens.
Remove from heat, add Cheddar cheese and whisk until melted.
Mix meat sauce and ziti in baking dish, stir in cheese sauce and sprinkle with Parmesan.
Cover and refrigerate for at least 7 hours.
:-Do not boil the pasta; it absorbs liquid during chilling. Heat oven to 350 degrees. Bake it covered for about 1 1/4 hours. Uncover and bake for 15 minutes longer until bubbly and lightly browned.