Evidently you don't want to do it the reliable way. Everybody wants a shortcut.
So try this VERY RISKY AND VERY UNOFFICIAL WAY:
0. Don't do this if you have ANY customizations to ANY of the PHP files other than the 2 configure.php files.
- backup everything and be sure the backup is reliable, since this whole "alternative" process is risky.
- delete all your Zen Cart files from the server, after copying the 2 configure.php files to your PC
- upload the new version files, and put back the 2 configure.php files
- run zc_install and choose Database Upgrade
- log into your Admin and remove and re-install all your shipping/payment modules, and of course re-entering all the settings. (If you skip this some modules won't work because new features have been added to them which won't be visible until you do.)
- Now redo all your images, language/text changes, template, logos, etc.
Doing it this way is really fast and simple, but your store will be OFFLINE the entire time until you're completely done. And you can't go backwards. And if you encounter errors/problems you won't have any way to allow purchases until you have fixed your errors/problems.
The longer official upgrade instructions insulate you from downtime and lost sales and from having your customers see any unpleasant errors, and from search engines deindexing your site due to errors.
Your choice.
I would never directly update ANY site (whether Zen Cart or not) without first testing the update in a COPY of the site to be sure there would be no gotchas or downtime or search engine penalties for errors, etc. But if you're willing to accept those risks, feel free to take the shortcut.