def calculate_max_diff(col_1, col_2):
    """Get a maximum difference between two columns

    Parameters
    ----------
    col_1 : Pandas.Series
        The first column
    col_2 : Pandas.Series
        The second column

    Returns
    -------
    Numeric
        Numeric field, or zero.
    """
    try:
        return (col_1.astype(float) - col_2.astype(float)).abs().max()
    except:
        return 0