Zip Archive – Create Zip Archive with Limited Number of Files

The argument of the function is $1.

You can use history expansion modifiers to extract the directory part and the last component of the path: if the argument is ~/directory2/directory1 then $1:h is ~/directory2 and $1:t is directory1. (Mnemonic: head and tail.)

Use parentheses instead of braces around the function body. This way the function body runs in a subshell (a separate shell process), and variable assignments, directory changes and so on only affect the subshell.

coolerzip () (
    cd $1:h &&
    zip -r $2:h.zip $2:h
)

Other shells don't have history expansion modifiers, so you'd need something different to parse the argument. For the file name, ${1##*/} strips off all leading directory components; however, this doesn't work if there's a trailing slash in the parameter, whereas "$(basename -- "$1")" works in that case. For the leading directories, use $(dirname -- "$1"). Note that in shells other than zsh, you need to put double quotes around variable substitutions.

coolerzip () (
    name="$(basename -- "$1")"
    cd "$(dirname -- "$1")" &&
    zip -r "$name.zip" "$name"
)

You're looking for zipsplit, it does pretty much what you're asking for. You'd create a ZIP file containing all your files, and then split it into files according to your requirements with zipsplit.

Something like:

zip -9 myfile.zip *
zipsplit -n 250000000 myfile.zip

would produce myfile1.zip, myfile2.zip etc., all independent of each other, and none larger than 250MB (in powers of ten). zipsplit will even try to organise the contents so that each resulting archive is as close as possible to the maximum size...

zipsplit is part of Info-ZIP's Zip, which is available as the zip package in all Linux distributions. The archives it produces are standard ZIP files; they can be opened without issue using other ZIP-compatible tools on other platforms.