My two cents...

Z strategies are mostly generic type (mean reversion, trend trading, momentum) so in the long term the'd be profitable and "everlasting". But, this doesn't mean they can have long periods of unprofitability or that certain assets perform worse in certain periods.

That's why they autocalibrate their parametes after a period of time, for trying to best adapt to market conditions.

You are right, luck is always a factor, so that's why you must diversify your assets/strategies, invest prudently (money management) and remain always flexible and vigilant.

There aren't any more secrets.

Hope this shed some light to you.