Local space rotation, why so hard!?

Hi, I’m sure this shouldn’t be a difficult thing to achieve but it has caused me a nightmare. I’m sure there is a simple solution I’m just not getting?

How can I retarget a world rotation from one object to another and apply it in local space? So if an object rotates in world ‘X’, how can I map that to another object’s local space so it matches.

I have messed around with the Transform Direction functions but I cannot get this to work.

Cheers!

I like to use localEulerAngles()