Bring a large saucepan of water to a boil; add cauliflower. Cover; cook for 10 minutes or until fork tender. Drain, reserving 1 cup cooking water. Place cauliflower in food processor or blender.
Melt butter in skillet over medium-low heat; add garlic and cook until fragrant. Remove from heat and add to food processor with cauliflower.
Add 1/2 cup reserved cooking water, milk, cheese, bouillon and pepper; cover. Process until smooth. Add more cooking liquid or milk if a thinner consistency is desired.
Using a spiral vegetable slicer, cut whole zucchini into spaghetti-like noodles. If you don’t have a spiralizer you can use a vegetable peeler.
Heat oil in same skillet over medium-high heat; add zucchini and cook, stirring occasionally, for 2 to 3 minutes or until softened. Add cauliflower Alfredo sauce and toss gently to coat. Season with salt and pepper if desired. Top with additional cheese and parsley.