ZIP files and filename encodings (with special characters) on different platforms is a well known issue that there exists no good solutions to- except making sure that both the sender and receiver is using the same encoding (program & platform).
We create the ZIP files on a Windows platform since most of our customers use Windows – but we are aware that this creates issues for Mac users when the filenames contains special characters (æøåôö etc).
If you create a ZIP file on a MAC containing these files – and try to unzip them in Windows you will experience the same issues – and vice versa.
The “solution” for us would be to replace ZIP files with RAR, TGZ, 7z or something like that. But this would create a shitstorm of support for us – since people would then need to install WinRar etc. in order to decompress the files. We might introduce RAR in addition to ZIP see how it goes.
But there is something you can do: Ask the sender (when dealing with these files) to make a RAR (or one of the other alternatives) archive and send this RAR file. This will decompress with the correct filename on all platforms.