Combine chicken broth, onions, parsley, oregano, chervil and salt and pepper to taste in large saucepan and bring to boil. Add zucchini and boil until tender, about 5 minutes. Transfer mixture to blender.
Cook peas in boiling salted water until tender. Drain. Add to blender and puree until smooth. Add sugar, horseradish and lemon juice and blend thoroughly. Mix in half and half. Cover and refrigerate at least 5 hours.
Adjust seasoning with salt and pepper. Ladle soup into bowls. Garnish with lemon and zucchini rounds.