>>>I have not tried it, but what happens when a tool such as WinZip (32 bit version) tries to create a zip greater than 2G? I would suspect that the problem is with 32-bit and the ability to access files greater than 2G in size (2**32). If this is the case then you will have to use a shell command and a 64-bit version of a zip compressor to create the zip archive file that is greater than 2G. You cannot call any active-x component that is 32-bit to create files greater than 2G.
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>>I wonder if that is true? I could zip a file larger than 2.5 GB, so the limit is not at 2G, which means it has nothing to do with 32-bit.
>>I will try the shell command, but it will be much more work to integrate, so I was hoping for some other third party tool that I could use.
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>Another question - what is the size of the resulting zip file when you zip a 2.5GB file? That may well be less than 2GB. But, maybe when you're zipping a 3GB file, the result wants to be greater than 2GB.
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>Exactly how large is the "corrupt" zip file?

The resulting zip files are well below 1 GB, mostly around 300 - 500 MB