def METHOD_NAME(proj_from, proj_to, arr):
    """
    Transform the x, y coordinates of the points but keep the z coordinate unchanged.
    """
    x = arr[:, 0]
    y = arr[:, 1]
    z = arr[:, 2]
    new_x, new_y = transform(proj_from, proj_to, x, y)
    return np.array([new_x, new_y, z]).T