There is a problem with the ZIP file.
Windows 10 extractor is unable to process the ZIP file at all.
WinZip finds one bad file (or filename) in the archive. The filename is clearly too long,
I replicated this problem after downloading the ZIP file a second time. So it was not corrupted during download.
Three lines from the WinZip extraction log:
Skipping file: unable to create a sensible filename out of "E:\DISTRIB\3D print\SmoothieWare\Firmware July 7 2016\Webif-pack-gh-pages (1)\Webif-pack-gh-pages\documentation\web\images\ker7egegneohm905wdu6x_uyyvwssoaoz6kwwbj9geoknhc1shkgnbf87bm-io3evwdnesy5pv2nizf1_pkoqvljlatpjqfvlmxgqcnjlhzul9vphbfrirz_0wigh4bilgp63ildtbqecpc4zk8yoktokttfbpgwnl2zd_dp0hferlncjd1w_nzzjtcmesejmswta2qbfdlhfdzrqhpwmu".