1st variant. CEO should add xyz.org with proper IP to the hosts file on his computer.
This will work on the local machine. However, if it is a laptop, and sometimes the same laptop will be used in intranet, you need another solution.
2nd variant. In hosts file, point abc.org to outer IP. On site, install plugin Multiple Domains and setup it to work with abc.org, too. Now your site is able to respond to xyz.org and abc.org. At home via VPN, CEO will be able to see site at abc.org address, and at work, over intranet, he will be able to see the site at xyz.org address.