def change_zp(flux, zp, new_zp):
    """Converts flux units given a new zero-point.

    **Note:** this assumes that the new zero-point is in the same magnitude system as the current one.

    Parameters
    ----------
    flux : float or array
        Fluxes.
    zp : float or array
        Current zero-point for the given fluxes.
    new_zp : float or array
        New zero-point to convert the flux units.

    Returns
    -------
    new_flux : float or array
        Fluxes with with a new zero-point.

    """

    new_flux = flux*10**( -0.4*(zp - new_zp) )

    return new_flux