Using a Mac app called [Hot link removed by moderator] ImageOptim, which is a front-end for the OptiPNG, PNGOUT, advPNG, Zopfli, Gifsicle, and MozJPEG tools, the total size of the Mac app bundle for version 2.1.3 can be reduced by 12%, losslessly. (A similarly large reduction should apply for the Windows installation.)
May I suggest adding the running of ImageOptim or something like it, on its highest settings, to the packaging process? It would save your download hosts on bandwidth costs—compression of the installation media won't be able to compensate for this—and your users disk space in every subsequent release.