Sauté the vegetables. In a large dutch oven, melt butter over high heat. Once melted, add onions, carrot and garlic. Cook until carrots are tender and garlic is fragrant. Season with salt, pepper and Old Bay seasoning.
Thicken the soup. Sprinkle flour over top and cook, stirring around the pot, until flour is cooked a bit, about 1 minute. While stirring, slowly pour in milk and chicken stock. Add chicken, corn and zucchini. Bring to a boil and allow to thicken.
Garnish. When ready to serve, stir in some fresh chopped dill.