That’s highly unlikely. The author is incorrect about it being a Zip file, it’s actually a simple gzip/zlib stream. Because it’s not possible to seek within such a stream, they are always chunked in any file that requires random access. Elsewhere there will be an index file which maps words to their corresponding chunks, so that the definition can be quickly loaded without having to decompress the entire file - or even load it all into memory. This is very normal stuff in the world of file formats.