What ways are there to clean dirty Ethereum? Is converting to Zcash and sending it with Z the best way? Do they use shapeshift to avoid exchanges? I'm curious to learn how the bad guys do it

Here's a good way to clean all your dirty laundry:

1. Buy XMR with your dirty ETH thru Shapeshift or Changelly.
2. Use xmr.to to get those XMR converted to Bitcoin.

Be warned tho that you won't get the optimal conversion rates for doing this process but it's the price you pay for cleaning off the dirt.

xmr.to keeps logs, so no dice. You need to transfer the XMR from wallet 1 to wallet 2, assuming both are offline wallets under your possession. Even then, there are no guarantees.

Yeah, I think that would be enough to hide your tracks. The only way to connect your connection with the other wallet would be for the authorities to get a hold of your view key. Plus the use of VPN's and TOR will hide your tracks with xmr.to enough that the authorities will have a hard time finding out who's who.

The people who are caught using the darknet for illegal stuff are the ones who fail to hide their tracks well. VPN + TOR + PGP is a must if you want to remain anonymous.