The PC will not be able to see these invisible extra parts, that is why they are zero length in file size.

In this scenario then any Mac connecting and using those fonts won't have problems with the zero byte length, because they were copied there from the Mac to the Windows server, and all the parts are there, whether it be older fonts with data and resource forks, or PostScript with screen or printer fonts. Mac fonts of any type that were copied to a Windows server or PC and he is connecting from a PC to that Windows server, or is trying to use them locally on that PC. The library that I am looking in is a network fileshare that has a font file with no bytes in it.