Additionally, if the editor works in English but not in other languages, it could be that the editor's language files for your language are missing. You will need to upload them.
What about HTMLarea?
HTMLarea is a very old, now obsolete, browser-based editor. It has been removed from Zen Cart in favor of offering you the choice of which plugin to install based on your preferences. The recommended choice is the more contemporary cross-browser-compatible plugin named CKEditor. You can find the plugin/integration files in the Plugins section of this site.