For editing, I suggest downloading a full backup of your Zen Cart files to your pc and putting them in an easy-to-reach place. Then install a good text editor like Notepad++. If you edit and save files there, then upload to your site, you will always have an up-to-date backup in case of server problems. Give Notepad++ and Filezilla (or whatever you use) icons/links in conveinent places on your computer screen, and it will quickly become easy to do it the right way. You will like the syntax highlighting, too, as it can show you when you have tiny fatal things like a missing '.