Question : Problem: wzzip -ys  switch

I have a zip file of 5 gigs , and I want to split this file into 02 zip files of 02 gigs each and another file of 01 gig.
I ran the following command:
wzzip -ys2000000 filenameX.zip   filenameY
after it has finished zipping, it gave me:
FilenameY.z01  
FilenameY.z02
they are 02 gigs each

FilenameY.zip
which 01 gig size.


My question is why those extensions  .z01  and .z02
what kind of extension type is this?  Is there aything I missed to get all of them with .zip extension?
thanks

Answer : Problem: wzzip -ys  switch

Ya, your first though was right, you open the main zip and then it asks for the rest, i do not belive it is possible to restore them seperatly.