Firstly i would try and see if you could separate the black zed badge from the silver backing as it will be alot easier to work with. If not you will need to mask up pretty neatly.
I would then rub it down with some 1200 wet and dry, then use a light coat of halfords grey primer followed by either an alimunium or silver paint and laquer OR some ceramic chrome paint (i got some from b&q), you won't need to laquer the chrome paint but the finish might not be as durable.
Once dried re-attach it with some 3M double sided sticky pads..job done
R