def get_atom_order_from_xyz(xyz):
    """
    Get the order in which atoms should be added to the zmat from the 3D geometry.

    Args:
        xyz (dict): The 3D coordinates.

    Returns:
        list: The atom order, 0-indexed.
    Returns:
        None: Not used, but important for returning the same number of parameters as ``get_atom_order_from_mol``.
    """
    atom_order, hydrogens = list(), list()
    for i, symbol in enumerate(xyz['symbols']):
        if symbol == 'H':
            hydrogens.append(i)
        else:
            atom_order.append(i)
    atom_order.extend(hydrogens)
    return atom_order, None