Please note that all files are provided with NO WARRANTY.
If you recive runtime errors, please download the Visual C++ 2005 Runtime Libraries Package:
The development thread of ZHLT 3 can be found here.
A subsequent development thread extending ZHLT 3.4 Final can be found here.
The development thread of these old tools can be found here.
The development thread for Merl's Half-Life Tools was previously hosted on the Valve ERC Collective site. However, this site sadly no longer exists.
There is a mostly untested ZHLT package for GNU/Linux, UNIX and POSIX systems and *BSD available here.
Vluzacn's ZHLT download contains source code of the latest version.
For earlier versions see ZHLT 3.4 final source code (source code archive).
See this list of other useful mapping software for mapping for Half-Life, including map editors and other tools.