Using a mandoline, slice the fennel very thinly. Using a vegetable/potato peeler, make ribbons with the zucchini (peel the outer skin off first and discard) and the carrots. Add to a salad bowl.
Chop the onion and parsley and mince the garlic, and add them to the bowl.
Add the sour cream, mayo, and lemon juice to the bowl. Toss the salad together and add salt & pepper to taste. Add some fennel fronds (the part that looks like dill) for garnish. Serve immediately or chill first.