ZIP archive files are handled by the OS...specifically BOMArchiveHelper. If you click once on the ZIP file and hit Command-I to bring up the Info box for it, what do you see in the "Open with:" section? I assume you see Script Editor. If you click on that menu, do you have BOMArchiveHelper as an option? If so, click that. Then you'll probably want to click the "Change all..." button to make sure that the OS opens all ZIP files.