I will be talking about two methods to study the SMBH-galaxy coevolution using quasars and strong gravitational lensing. 1) Reverberation mapping of lensed quasars: Reverberation mapping is a method of measuring the masses of the SMBHs at the center of quasars with long-term spectroscopic monitoring. Strongly-lensed quasars are excellent targets
for reverberation mapping, because the monitoring period can be decreased thanks to time delays between the lensed images. I discuss the prospects of performing reverberation mapping on a large sample of lensed quasars. 2) Quasar host galaxies acting as strong gravitational lenses: Host galaxies of quasars are difficult to observe and understand mainly due to the sheer brightness of the quasars outshining the hosts. In the extraordinary case of a foreground quasar host galaxy lensing a background source, the gravitational lens system can be analysed to
determine the mass of the host. I discuss the current status and future of the High-z Universe probed via Lensing by QSOs (HULQ) project.