import re


def homogeneize_phone_number(numbers):
    """
    Homogeneize the phone numbers, by stripping any space, dash or dot as well
    as the international prefix. Assumes it is dealing with French phone
    numbers (starting with a zero and having 10 characters).

    :param numbers: The phone number string to homogeneize (can contain
        multiple phone numbers).
    :return: The cleaned phone number. ``None`` if the number is not valid.
    """
    if not numbers:
        return None

    clean_numbers = []

    for number in numbers.split(','):
        number = number.strip()
        number = number.replace(".", "")
        number = number.replace(" ", "")
        number = number.replace("-", "")
        number = number.replace("(", "")
        number = number.replace(")", "")
        number = re.sub(r'^\+\d\d', "", number)

        if not number.startswith("0"):
            number = "0" + number

        if len(number) == 10:
            clean_numbers.append(number)

    if not clean_numbers:
        return None
    return ", ".join(clean_numbers)