Zope is using Python's "logging" module and wants to play well
with log rotating (start a new logfile, do something with the old log file
(compress, rename, remove)).
It does this by registering a signal handler which closes its logfiles
when the corresponding signal is received.
Maybe, you can do something like this. Signal handling under
Windows is limited, but maybe you find a usable signal under Windows
(Zope is using "SIGUSR1").