I won't answer this, because it's getting late.
However I'll give you one word of caution, and one piece of advice, both of which might help you shape the flow yourself!
So, word of caution: Watch out for looping here, as if you're having a trigger or triggers on additions or modifications to either list, which are then modifying or creating in the alternative one ... you will have problems. So pick your logic wisely. 🙂
The piece of advice is something that I think will probably really help you to realise how you can get the 'difficult' part of this to happen a lot more easily. You need to add something to your SharePoint lists that you may not yet have done.
For each lookup column, just include an extra column which contains the ID column. This will allow you to easily act on any array of items passed into Power Automate.
But wait?!
Do you need to use Power Automate? Look a bit lower, what is that which I spy?
Deletions from source list affect this list
and
Deleting source items deletes values in this list
These will really help you with your problem, here, meaning that it takes care of any deletion logic that you were worried about handling.
It's a shame, because I remember that the lists of old could have much more interactive levels here.
You might still be able to accomplish that, though, using SharePoint Designer 2013 if you can find it. 😉
