I am using QuaZip library, which has zlib dependency. I want to compile my CMake managed application under Archlinux and Windows 7, in both I have Qt 5.3.0 installed.
Try to add into pro file this line:
INCLUDEPATH += $$[QT_INSTALL_PREFIX]/src/3rdparty/zlib
or
INCLUDEPATH += $$[QT_INSTALL_PREFIX]/src/qtbase/include/QtZlib
INCLUDEPATH += $$[QT_INSTALL_PREFIX]/src/qtbase/3rdparty/zlib
For my app this worked fine.