I have experienced these differences with lots of breakout systems in 5 min charts. The performance can vary arround 10% on a day in different accounts of the same broker on different servers or if the base currency is not the same. I use a high quality broker (ecn/ndd).

If you use 1 min charts indicators can be different more likely than when you use daily charts.

As I understand the z systems seem to depend heavily on the start and training period for the first days of trading.