Zip makes different tradeoffs. Its compression is basically the same as gz, but you wouldn't know it from the file sizes.
Tar archives everything together, then compresses. The advantage is that there are more patterns available across all the files, so it can be compressed a lot more.
Zip compresses individual files, then archives. The individual files aren't going to be compressed as much because they aren't handling patterns between files. The advantages are that an error early in the file won't propagate to all the other files after it, and you can read a file in the middle without decompressing everything before it.