I would reduce the margin in the new account by the same percentage as the capital was reduced. When the trades in the old account are closed and the rest capital is transferred, the margin can be increased to the previous value.

Why should Z3 not open a trade dependent on your balance? Z3 does not even know your balance. The balance also has nothing to do with test results or required capital. The required capital is based on statistical risk, not on the stop distances of single trades.

http://manual.zorro-trader.com/performance.htm