Spectral evolution of AT 2020zso from early to late times. All spectra are continuum normalised. The different emission features in the 4600 Å blend are indicated with vertical lines: solid black lines indicate H Balmer lines, dashed black lines N III, dotted black lines Fe II, red dashed lines He II, and red dotted lines He I. Black spectra were taken with NTT/EFOSC2, blue with VLTX-shooter, orange with LCO/FLOYDS, and magenta with NOT/ALFOSC. The X-shooter spectra are resampled at lower spectral resolution for clarity. The gap around 5200 Å is due to the low S/N of the data at the edges of the UVB and VIS arms, and the gap around 7300 Å is due to the poor correction of molecular bands.