Both Margin and Risk affect the profit and the required capital. So just click [Test] with different settings until you end up with the capital you want to invest. It will be different for Z1 and Z2.
You can normally run two Zorros simultaneously on the same PC. According to FXCM this won't work, but we found that it works when Zorro logs out every weekend, which it does with Z1 and Z2.
See also What's new for the wake-up bug of the current version:
http://zorro-trader.com/manual/en/new.htm