Good question, and yes – it's a technique some people use, though not for everyday transactions because of the costs and time. The logic is that each mixer has its own liquidity pool and mixing algorithms. If you use one, your coins mix with other users of that service. If you then pass them through a second mixer, they mix with a completely different set of coins, breaking any possible correlation left from the first. Some even add a third for maximum paranoia. The trick is choosing mixers with complementary features – for example, one that excels at many output addresses like ChipMixer, and another that specializes in speed or coin quality like MixTum. The key is planning intermediate addresses and timing carefully to avoid mixing up transactions. To understand which mixers combine well, I recommend reading this https://bitcoin2.biz/best-bitc.....ixers.html guide that compares all the services and explains their unique strengths.