What is the ZTK: http://docs.zope.org/zopetoolkit/
In Debian and Ubuntu, the ZTK is packaged as a set of python packages. e.g. python-zope.interface.
Currently, for wheezy, we are targeting the versions included in the ZTK 1.1 (Mailing list thread). This means that there must be no upload of new upstream release whose version are not listed on the page given before.