C IV EW as a function of the C IV–Mg II velocity shift for seven quasars reported in this paper. The dark blue triangles represent z>5.7 quasars from Shen et al. (2019), Schindler et al. (2020) and Yang et al. (2021), and the light blue stars show the WLQ samples of Wu et al. (2011), Luo et al. (2015), and Plotkin et al. (2015). The gray contours and gray dots show the low-z comparison sample at 0.35 <z< 2.25 from the SDSS DR16 catalog of Wu & Shen (2022). Our sample generally follows the high-z quasars distribution. The only exception is the quasar PSO J041+06, which shows a velocity shift >9000 km s⁻¹ and an EW value of 6 Å, typical of a WLQ. The only object similar to PSO J041+06 is J1219+1244 at z= 2.233.