Place leeks in a large bowl of cold water and let stand for about 5 to 10 minutes. Lift out of the water, drain, and set aside.
Cut squashes in half lengthwise; remove seeds. Peel and cut into 1/2-inch dice.
In a large saucepan over medium-low heat, cook leeks in 2 tablespoons of water until they soften, about 10 minutes. Add squash, orange zest, and spices; cook for 2 minutes. Add 5 cups chicken stock, salt, and pepper; stir to combine and cook for 20 to 25 minutes, or until squash is tender.
Puree in a food processor in 2 batches. Return to pot; reheat and add more stock to thin to desired consistency, if necessary. Serve garnished with Jicama Salad (recipe follows), if desired.