I want to achieve following rule

`...a b c d...->c d... ...a b`

I have tried function `substitute`

, but I have no idea how to achieve it. My recent work need this operation. Are there any suggestions about it?

For example, everything is `NonCommuting`

and `depends \partial{#}`

in following formula
$$
a b \partial_{\mu} c d
$$

I must exchange $a b$ with $ \partial_{\mu} c d $ to get

$$ \partial_{\mu} {c} d a b $$

then use `substitute`

or `integrate_by_parts`

to get

$$

- c \partial_{\mu}(d a b) $$

I am trapped in this point now.