Unfortunately this fileset seems to have become corrupted somehow. Many of the tracks feature skipping and glitching during playback, which makes the whole OST pretty much impossible to use. A great shame since this is an extremely well-made collection, but if the music doesn't work, then there's no point.
edit: Just testing things: the files play perfectly when streamed through the archive, but are corrupted upon downloading. Downloading individual tracks or the .zip doesn't matter, both methods produce a glitched version.