Zope SSL Integration - Others
Going by the number of howtos published, the most common way to integrate Zope and SSL is to run Apache + mod_ssl as a reverse proxy for Zope. This method also uses the Apache modules mod_rewrite and mod_proxy.
Others have also used the Squid proxy/cache/accelerator as an SSL reverse proxy for Zope. Some people may have used Squid to front Apache to front Zope.
Pound is a reverse proxy, load balancer and HTTPS front-end for web servers. Pound was written for Zope originally. Its z2s.py patch looks rather like ZServerSSL's. ;-)
Nihongo ga wakarimasen, but I've seen a ZServerSSL-like effort called zSSL from Japan. Appears to be abandonware.
On Windows, there are tools to integrate IIS and Zope. These should allow IIS to act as an SSL reverse proxy for same.