I can confirm I made the very same error, thinking the listed zip file name (with its firmware revision description as its file name) simply needed renamed to update.zip after downloading directly on the Himedia (Q5 in my case).
I realised myself the downloaded zip my 'contain' a further zip file...which proved to be the case when I took it to my PC.
As per the above post, once I extracted the update.zip file and went back to the Himedia Q5, it updated perfectly...takes a wee while so be patient :-)
Steve.