If it doesn't already exist, I think you just created a product. An easy to remove full laptop sticker that looks like the laptop, and allows you to put on other stickers, then remove the whole thing leaving no traces and protecting from sun bleaching. I bet this is already a thing.
[edit] It somewhat exists. I found "macbook skin's" on amazon.
A good solvent-based adhesive remover should be able to take those marks off. I can recommend De-solv-it "sticky stuff remover" but I have no idea if that's available everywhere. It has a silly name but it works very well.
Actually there isn't any residues left on the surface, it's perfectly smooth without any asperities. I wonder if it has been caused by the effect of the sun? Because the marks really looks like decals now...
Those markings are caused by uneven sun bleaching due to the stickers blocking U/V radiation to varying degrees of effectiveness.
So they can’t be removed, right?
Unfortunately, no. It's UV damage to the shell that would normally be even across the entire surface (and thus not really noticeable).
Anodised aluminium is kinda porous. Penalty some of the solvents have entered the material. Maybe you can get it out with more solvent. Or maybe it'll make it worse...