Integrated spectra from the MUSE data cube with apertures shown in Fig. 4. The binned flux is computed by imposing a minimal S/N of 5 per wavelength bin. From top to bottom, Lens centre: from left to right, the stellar absorption lines CaH, CaK, H[[INLINE557]], and G-band (orange dashed lines) are consistent with the previously determined z_d = 0.729. P5: from left to right, the galactic emission lines Ne III, He I, H[[INLINE559]], and H[[INLINE560]] are highlighted with green dashed lines and allowed us to measure z₅ = 0.3575. We also identify the stellar absorption lines H[[INLINE562]], HEI, CaH, and CaK allowing a velocity dispersion measurement. P6: from left to right the lines Mg I, Ca II O II, H[[INLINE563]], and O III doublet allowed us to measure z₆ = 0.505. Quasar images: from left to right, we recognise the C IV, C III, C II, and Mg II emission lines.