Unzip file containing zip files

I have been able to successfully get the contents of zip files using this query from Mark Whites Blog.

However, this does not appear to work when applied to a zip file that contains multiple zip files itself. In this case it only seems to obtain one of the contained files.

I am assuming this is somehow caused by the following condition (and subsequent filter on IsValid):

if _ <> 67324752             // not the IsValid number? then return a dummy formatter
            then BinaryFormat.Record([IsValid = false, Filename=null, Content=null])

Any ideas on what is happening and how to fix?

Thanks!