which is which
(informal, especially as a question) Used to indicate multiple things are difficult to tell apart
In real life, the hardest aspect of the battle between good and evil is determining which is which. George R. R. Martin
Body and spirit are twins: God only knows which is which. Algernon Charles Swinburne
We make messes of our lives, but every now and then, we manage to do something that's exactly right. The challenge is figuring out which is which. Jodi Picoult
I suspect there's little difference between whim and inspiration at the beginning of any chain of events. It's what happens later that tells us which is which. Sheri S. Tepper
I've got the Jewish guilt and the Irish shame and it's a hell of a job distinguishing which is which. Kevin Kline
Much of what we do at any level is a bit like that, I fancy. But hard to know which is which. Ted Hughes