What is the purpose of the splitting? If you just want to split it into chunks to fit on some media, you could use "split". You can later re-constitute the full file by using cat.
If you want the three parts to be valid zip files in themselves that is trickier. If I had a need for such a tool, I would consider using "dar", which is a little like tar, but has lots of extra features like spanning archive files over media and the like.