No, it isn't. It is more concentrated in time, but the total energy is not as different as you think.
A standard zapper running the standard 7-20-7-20-7 pattern delivers between 70 and 80 W-s (watt-seconds) of electrical power to the body (and approximately the same energy into the 1 K ohm output resistor.
ECT devices deliver up to 800 mA pulses for 1 to 6 seconds, and are capable of delivering several hundred watts. So a light dose of 100 W for 1 second would be 100 W-s, approximately the same as a zapper session.
1000 times more concentrated - yes.
1000 times more powerful - no. On average, more like twice.