issue fixed by assigning static public (external) ip to GCP VM. Once VM established connection to internet it was able to download required packages.

Steps to follow to enable xclock on Google cloud platform - Compute Engine

1. Assign public ip
2. Login using root (sudo su – root)
3. Run below commands,
a. zypper install -t pattern gnome-basic
b. zypper install xrdp
4. Install putty -
5. Enable X11 in putty. (Putty main login page, before login to system)
6. Install Xming -
7. Double click “Xming”, that’s it
8. Open putty,
a. login with root
b. export DISPLAY=
c. xclock
9. if any issues with host/protocol
a. run command xhost + (This gives access to all hosts)
b. export DISPLAY=:0
c. Manually add entry to “C:\Program Files (x86)\Xming\X0.hosts”
d. Restart Xming and putty

Hope this help someone looking for an similar issue.