One thing I’ve noticed, which probably somewhat understandable, is that most people still think “zip” when they need to compress something. A lot of the time this makes sense, it’s the one file format that you can guarantee the other end supports, and you can get support for it as part of libraries for every programming language.
Unfortunately it’s not that good as a file format. Partly in that it doesn’t compress as hard as other formats, but mostly because it doesn’t compress between files, only inside them. So if you’re compressing hundreds of identical files, you’re compressing each file by itself and then adding it to an archive, instead of compressing the identical portions first and then only worrying about the differences in each file after that is taken care of. Even with that aside, the 7z format is just better.
Let me demonstrate with an exe file, something that you would normally think wouldn’t be that compressible.
The original and uncompressed file is the largest, zip is the second, and 7z is the very smallest format. If you’re curious I also tried it with bzip2 and xz, both formats ended up larger than 7z in terms of file size.
The Windows software that does this is called “7-zip” and you can get it for free here.
Not the best choice for transferring over the internet, but a better choice for longer term file storage on your own systems.