def zip_codes_to_go(target: list, zip_code: list) -> list:
    """finds the zip codes that haven't been used

    Args:
        target (list): the list of zip codes that you want
        zip_code (list): the list of zip codes that you already have

    Returns:
        list: list of zip codes that you still need
    """
    
    combined = target + zip_code

    for code in target:
        if (combined.count(code) > 1):
            combined = [i for i in combined if i != code]
    
    return sorted(combined)