Zsh 5.0 is the first major stable release since version 4.2, which was released in 2004. The announcement states that many changes have been made since the last stable release series, of which the most important is support for multibyte characters.
Other new features of the 5.0 release include: support for highlighting and coloring of the command line, job control support in non-interactive shells and subshells, and an improved zshroadmap manual page. Additionally, improvements have been made to Posix compatibility when the shell is in a corresponding emulation.
A full list of new features is available in the NEWS file for the release, and the README file notes some incompatibilities with previous versions. The latest version of zsh can be downloaded from the project’s mirrors and FTP server.