To install this extension, open Notepad++ and go to Language -> User Defined Language -> Define Your Language... -> Import and select whichever file(s) you want to use.

It will import with the proper version label. You might need to manually selected from the User Defined Language drop-down though.

It should auto-select when opening a .zs file, but if it's not working let me know (and if you know how to fix it, please tell me).