For cad/zinc-coated spokes, I stay away from the abrasive cleaners like Simichrome. It's got some very harsh abrasives for cutting through chrome, you can feel the grit when you use it.

I prefer to use a chemical-cleaner/polish like Mothers or Blue Magic. These are ammonia-based metal cleaners that take the minimum amount off. Will only give the coated spokes a clean light-grey finish, which is the best you can expect. If you want shiny, then gotta rebuilld wheel with new stainless spokes.