The zapper works just fine. The pharmacutical cartels have just hire 15-20 people to work here on curezone and say they don't, so it seems "everyone's" failed at using them It's called establishing a 'norm'.
The zapper doesn't kill parasitic worms (at least not the big ones). The zappers sellers cartel have just hired 15-20 people to work here on curezone and say they manage to kill all kinds of parasitic worms in all parts of the body, easily, quickly, without side effects, so it seems everyone succeeded at using them. It's called establishing a 'norm'.