Poco 1.5 is already updated to use zlib-1.2.7.
Please consider updating Poco 1.4.5 to use the same version of zlib.
This won't make it into the 1.4.5 release, as I've already done all the testing, etc. and I don't want to delay the release any longer. Planned for 1.4.6, in January, though. If it's urgent, create a branch here and merge in the change from develop branch.
1.5.2 and 1.4.6p2 will include zlib 1.2.8