Further work on the NexusVR application has required me to find a solution to handle zip files. Having found no suitable alternatives, I decided to port 7zip to UE4. This resulted in the ZipUtility plugin.
Fully multi-threaded and exposed to C++ and Blueprint, it allows for easy extraction and progress update.
From 7zip support for many file formats are available such as Zip, 7-Zip, GZip, BZip2, RAR(decompress only), TAR, ISO, CAB, LZMA, and LZMA86. This and some utility windows file API functions means that it should serve my needs well and I hope you UE4 developers will find good use for it!