# assuming /mnt/root/{root,home} are mounts of anothers system root+home filesystems

cd /mnt/root/root
mount --bind /proc proc
mount --bind /sys sys
mount --bind /dev dev
cp /etc/resolv.conf etc/
cd /mnt/root
mount --bind home root/home
chroot root /usr/bin/zsh

# leave via Ctrl+D (EOT), exit