Nitpick: RAR/7Z are formats.
WinRAR and 7-Zip are programs that handle ZIP/RAR/7Z
Seriously, try out advzip -- I think you will be pleasantly surprised.
Zopfli is the new kid on the block, but it has quickly taken the crown for efficient ZIP compression. Beating out 7-Zip's DEFLATE algorithm as well as KZIP.
Code:
advzip.exe -z4 -i 500 ZIPFILES...
advzip.exe --recompress --shrink-insane --iter 500 ZIPFILES...