Hmmm, i’m starting to be afraid of something.
I’ve printed the three available translation of FString into std:string:
And only the first one is correct:
The UE4 encoding doc says FStrings are UTF16, which gives sense to the above result: the constructor FString will read UTF8 and ANSI as UTF16, hence the wrong displays.
Now, Windows uses UTF16, so the file name should be encoded in UTF16, so i think the TCHAR_TO_WCHAR macro should be used.
But the AddFile function in the library i use (which leads to the AddEncrpytedFile herebelow) takes only std:string (so ansi or utf8) as an input and use it in std::ifstream::open():
But it looks that std::ifstream::open() only works with *char or &string:
http://www.cplusplus.com/reference/fstream/ifstream/open/
But to work with UTF16 i would need a function capable of working with std::wstring, which is not the case here.
So i’m afraid that ZipLib can’t work with UTF16 and is simply not compatible with Windows.
I hope it’s not that and i don’t have to go hunting another zip library that i can embed in my code.
Finding this one was nightmarish enough !
Anyone can see a flaw in my reasoning ?
I really hope so 
Thanks
Cedric