I haven't seen anyone post this, so here goes from http://www.zhlt.info/ :

ZHLT 3.0 final was release on 4th Feb 2004.

This release of ZHLT fixes the serious problems in XP-Cagey's final p15.5 version version of the tools (these included a very slow RAD, incorrectly-cast entity shadows, and overbright light_environment).

These compile tools are derived from XP-Cagey's p15.5 source, which were derived from Merls custom build 1.7. This was in turn derived from Zoner's Half-life tools build 2.5.3.

This version of the tools was written by amckern, who has now moved on to writing improved versions of the Source compile tools. Please visit his ZHLT/CST site to download ZHLT 3.0 or CST.

This ZHLT-version seems to never actually be tested, as users keep reporting that HLRAD crashes.

so true Zyndrome

hmm I saw this a while ago and last time I looked there was a note on the website saying 'these tools have an error it will be resolved shortly'. As that message is now gone I thought they'd fixed it. I guess not...