I found the answer. To be able to install Ubuntu at all on HP zbook G3 laptop, follow the referred post above. In this post the discrete graphics setting (setting 1) needs to be chosen in the BIOS. As far as I know, this setting does NOT allow to switch between two different graphic cards. Running the command
lspci -k | grep -A 2 -i "VGA"
,
does only show my Quadro dedicated graphics card, not the Intel integrated graphics card.
However, AFTER the Ubuntu installation, you can change back to hybrid graphics in BIOS (setting 2). I have not tested setting 3: Auto in BIOS. Using setting 2 in BIOS allow us to switch between the dedicated graphics card and internal graphics card as described here:
https://www.linuxbabe.com/desktop-linux/switch-intel-nvidia-graphics-card-ubuntu
By running lspci -k | grep -A 2 -i "VGA"
, now both my graphics card are shown in the output.