Files extracted OK for me. I am aware of someone else who has been finding the download to be corrupt but perhaps the download process itself went wrong?
Probably not relevant but the current (19/12) download contains over 1000 bus timetables, compared with the normal 700 or so. This seems to be because of the way the system deals with the Christmas period, uploading oodles of one-day-only files.
What the download does not contain is anything for New Year’s Eve night services on what are normally just day routes. Presumably there won’t be another set of files created before NYE. The TfL website refers (or did last night anyway) to services on “selected” day routes without specifying, so the poor old passenger or third party user is left in the dark.