Add water to a large pot fitted with a steamer basket, just enough to reach the bottom of the basket. Place carrots, cauliflower, and zucchini into the basket. Cover and steam for 15-20 minutes until fork-tender.

Transfer the steamed veggies to a blender and add 1 cup of half-and-half. Blend for 2-3 minutes until smooth and creamy. Strain the mixture through a fine mesh strainer and set aside.

Cook the elbow noodles according to the package instructions until al dente. Drain well.

In a large saucepan, melt the butter over medium heat. Whisk in the flour and cook for 2-3 minutes, whisking frequently, until golden brown and thickened.

Gradually whisk in the remaining ½ cup of half-and-half, stirring and heating until it begins to simmer, about 2-4 minutes.

Stir in the strained veggie puree and salt. Bring the mixture to a low boil.

Add the shredded cheeses, one handful at a time, stirring well until completely melted. Cook the sauce for 1-2 more minutes until thickened.

Pour the cheese sauce over the cooked noodles in a large pot or serving bowl and gently fold everything together until evenly coated.