If I have coins in ETH1 address and I create ETH2 on same wallet, how can I transfer coins from ETH1 to ETH2 to ensure people who knows ETH1 lose trace and make coins private in ETH2 again?
For example I have 10 coins in ETH1, then I transfer 1 to Coinbase, then Coinbase knows that I have 9 coins in my wallet. How to make that 9 coins private again?
The obvious answer is to use a mixer/tumbler. The best option for Ethereum right now is probably Tornado Cash. Despite being decentralized and smart contract based, it has fairly impressive liquidity.
https://tornado.cash/To mix BTC, I'd go with Chipmixer.