Hubble diagram of SNe Ia (cyan points), quasars (yellow points), and GRBs (black points) with the 1σ uncertainties. Red points are the mean (also with 1σ uncertainties) of the distance modulus in narrow redshift bins for quasars only (shown for visualisation purposes). The dashed magenta line shows a flat ΛCDM model fit with Ω_M = 0.3. The green dotted line is the best MCMC fit using the standard cosmographic approach (Sect. 3.1) with the inclusion of GRBs and Pantheon, whilst the blue dot-dashed line represents the new regression fit (Sect. 3.2). The black solid line is the best MCMC regression curve of the third-order expansion of log(1 + z) published by RL19 and obtained by fitting the quasars and the SNe Ia from the JLA survey (Betoule et al. 2014).