Black hole mass from Mg II versus dynamical mass for our four quasars with [C II] S/N ≥ 5 detections (teal data points) and for other high-redshift quasars from various literature works (golden data points; Feruglio et al. 2018; Pensabene et al. 2020; Neeleman et al. 2021; Tripodi et al. 2024; Bañados et al. 2024, 2025). Systematic uncertainties of 0.5 dex on both black hole and host galaxy dynamical mass are reported in the bottom right corner. The gray solid line is the local relation between black hole masses and galactic bulge masses from Kormendy & Ho (2013), and its 1σ uncertainty is displayed as a shaded region.