NoCan anyone tell me if you can remove the door speaker without taking the door card off please?. I’ve recently bought a Z4 and it looks like someone previously has spilt coffee on it !!
I would try a damp old toothbrush and a bit of soap solution.That's not the actual speaker - it's a metal mesh cover.
Squirt a bit of all purpose cleaner (anything from the kitchen cupboard) on a soft bristle brush - that will either clean right up without removal, or you will find out it is rust.
If rust - you will need to get the door card off & repaint.