After a long fight, I managed to install Zorin 16.1 and then upgrade to 16.3 (there is still no option to upgrade to 17 core yet)
What I did was :-
- Select Try Zorin
- Then Disconnect the internet
- Mounted some of drives (I had mounted the one in which I had to install Zorin)
- Then idk if its necessary but I had changed my theme to Adwaita (I had done all these process without this one and it hadn't worked. So you can give it a try)
- Then I started then the Install Zorin which is on Desktop.
After selecting my keyboard layout, zorin asked me to dis-mount my all mounted drives. I allowed it and bang, the process was once more smooth as butter. Zorin got installed in just few minutes.