By the way -- why did you put the option "w" into "-xwzf"?
Previous suggestions stated "-xvvzf" (though admittedly the repetition in "vv" is redundant: you can just as well use "-xvzf"); maybe you misread "vv" as "w"?
Ah! Checking the man page (thanks Ted) it all becomes clearer. It is v v
Well, you live and learn. I shall report back later.
cheers Bev.