Split a Zip file, combine, and unzip- Linux

You have existing.zip of say 3G but want to split it into 500M sized parts.

zip existing.zip --out new-split.zip -s 500m

will create

new-split.zip
new-split.z01
new-split.z02
new-split.z03
....

To extract them, you should first collect the files together and run

zip -F new-split.zip --out existing.zip

or

zip -s0 new-split.zip --out existing.zip

to recreate your existing.zip, Then you can simply

unzip existing.zip.