Yes, that's what i found today , the bug seems to reside in zlib code.I think that answer is in zlib.
If all contents in pk3 file is extracted and then chdir("../../xxxx") is used before before getMesh() function all is ok.
Moreover it's related to the pk3(zip) file size , if the archive is bigger than
~3 mb(on my computer), the zlib extraction code compiled with BCB doesn't work as expected and GetMesh function fails...
Other than that BCB dll seem to work ok, and it builds the engine with smaller size than the original Irrlicht.dll compiled with VC++ as well as the import library , plus the ability to use a RAD IDE with great database support and literally thousands of open source components to make editors and tools really makes me want to sort all bugs out.