I have looked at the file and this is what I found. Your epub file is not quite proper zip file. Normal zip files should start with the sequence "PK\3\4" and your file starts with "PK00". This might be a marker that zip splitting is allowed - I am not sure, at least many zip utilities can process it.
In any case, this is not a valid epub file. OCF spec has a very strict rule on the extra headers in zip format (they are prohibited). I have looked at our code and I am pretty certain that this file could not have ever worked in Digital Editions (1.0 or 1.5). I think something changed in your process. Look carefully into WinZip options.