The thumb and flash being similar is a clue that it probably isn’t the category, although flash drives are more generally any type of drive with flash memory that connects through USB, and thumb drives are mostly referring to those small USB sticks. But zip is a physical drive (a separate thing from a zip file). It was only around for a few years in a sort of awkward limbo between floppies and CDs https://en.wikipedia.org/wiki/Zip_drive