Zope was for Python 1.5.2 (quoting the README from https://old.zope.dev/Products/Zope/2.0.0-donotuseme/2.0.0/Zope-2.0.0-src.tgz https://old.zope.dev/Products/Zo

Zope was for Python 1.5.2 (quoting the README from https://old.zope.dev/Products/Zope/2.0.0-donotuseme/2.0.0/Zope-2.0.0-src.tgz https://old.zope.dev/Products/Zope/2.0.0-donotuseme/2.0.0/Zo... - "This release requires Python 1.5.2."). Python 1.6 was a "contractual obligation" release that few used, when compared to 1.5.2 or 2.0. See https://python.readthedocs.io/en/v2.7.2/whatsnew/2.0.html#what-about-python-1-6 https://python.readthedocs.io/en/v2.7.2/whatsnew/2.0.html#wh... . 1.6final and 2.0beta1 were released on the same day, and 2.0final was released a month later. The 2.x series was almost completely backwards compatible to 1.x.