Remove Workgroup & Zscaler off Refurb Dell Optiplex 9010

Following https://www.ozbargain.com.au/node/388105 ,

I'm able to login the win7 and decided not to wipe the OS as I want to retain the MS office suites.

So what is the proper steps to turn it into home use ?

Is there a way to remove the workgroup/domain and setup new user account ?

and how to remove the Zscaler network program (which prompted password to uninstall)

Thanks.