I guess that you are referring to the blood electrifier?
The main difference between the zapper and the blood electrifier is that the zapper is intended to work across the entire body while the blood electrifier is designed to increase the bulk of the electrical signal into the blood as it flows through the arteries and veins.
Some people claim that the zapper does not penetrate but that is mostly because they have not tried a strong enough zapper with the correct electrodes. Many people who have tried zapping with better zappers and a 4 point contact system with 3 points positive have noticed that they can reach intestinal organisms. As evidence of this, many have to replace their normal intestinal flora / fauna after zapping.
You might want to read " parasite Zapping and the Zapper" to learn more.