There's a rival trojan on the market it's called spyeye. It costs 600$.
Spyeye is cheaper.
If a computer is infected with the zeus trojan and the spyeye trojan at the same time, the person controling the spyeye trojan can kill the zeus trojan. with a function called "kill zeus". What do you think about that now?
Be careful not to buy any trojan from an untrusted seller as many are backdoored.