As I was tired to unzip my test .docx files to see what was inside, I decided to ask the web for a solution. I have been gladly surprised to see that Vim can natively open Zip files and change them. All I had to do is to tell Vim, that the docx, odt, and other OpenXML and ODF extensions are Zip files. Here are the lines I have added to my .vimrc file:

au BufReadCmd *.docx,*.xlsx,*.pptx call zip#Browse(expand(""))
au BufReadCmd *.odt,*.ott,*.ods,*.ots,*.odp,*.otp,*.odg,*.otg call zip#Browse(expand(""))

Now debugging life will be easier for me, and maybe for you too.