[rocqua]

The second spend in your double spend needs to be before the re-org is noticed. Make that spend a swap to Zcash / Monero and you can't be traced. So a full scenario would be:

* Swap coin for Zcash and start mining with 51%. * Wait until your chain is longer than the main chain, and you actually hold the Zcash. * Publish the longer chain, and immediately swap your spent coin for Zcash again. (At a different exchange just to be sure).

Now, you got twice the value of Zcash you needed, and due to Zcash shielded transactions can't be traced. You just have to hope that your shenanigans won't tank the value of Zcash.

Similar things could be done with Monero.