No, it won't. Both PNG and JPG files are already compressed so you can't gain much on this. You'll gain a bit more with .rvdata files but not enough for 73% performance.
To be certain, I tried 7Zip Ultra compression on a 4.5 MB demo (without any sound effect or music) and it was 3.6 after compression. You can hope to gain size with WAV files though - if you have SE at WAV format, convert it to OGG. If you have even one mp3 track, convert it to OGG as well (with Audacity
). Other than that, there's nothing to do.
But then again, 7.5MB is small.