'Comoving line-of-sight distance in Mpc between objects at
redshifts z1 and z2.
The comoving distance along the line-of-sight between two
objects remains constant with time for objects in the Hubble
flow.
Parameters
z1, z2 : array-like, shape (N,)
Input redshifts.  Must be 1D or scalar.
Returns
d : `~astropy.units.Quantity`
Comoving distance in Mpc between each input redshift.'

def _comoving_distance_z1z2(self, z1, z2):

    from scipy.integrate import quad
    f = (lambda z1, z2: quad(self._inv_efunc_scalar, z1, z2, args=self._inv_efunc_scalar_args)[0])
    return (self._hubble_distance * vectorize_if_needed(f, z1, z2))
