FEAD Compressing Compressed Files by 50-75%?

An anonymous reader asks: "I just installed Acrobat Reader and found that it was using FEAD which claims - 'FEAD© Optimizer© significantly reduces the size of application programs on average by 50% (in some cases up to 75%, depending on the specific software), even when they are already compressed with common compression technology like ZIP or CAB.' . It seems that they optimize each application individually at thieir labs. But an average of 50% compression on already compressed binary files seems to be too good to be true. Anyone familiar with how someone may be able to achieve this?"