Zip file inside Zip file(s)

UNIX for Advanced & Expert Users
1

I've a zip file called Z00.zip and in that file there are 22 more zip files. Each zip file having .txt files nearly 10,000 files. I am trying to unzip all these .txt files in one command line to unzip each .zip file from Z00.zip file. Would like to know whether possible to unzip all sub-zip files from Z00.zip in one command line. My zip file structure is like,

==> Z00.zip
=====> 00.zip
=====> 11.zip
=====> 22.zip
=====> 33.zip
.
.
.
=====> 89.zip

How to unzip all these sub-zip files in one attempt?

2 
unzip Z00.zip
for FILE in [0-9][0-9].zip
do
        unzip "$FILE"
done