If they are wanted clean but not shiny you may want to try ketchup if will make it smell like the ketchup and lemon juice will do the same but make it shiny but acids take some copper off both pure copper and zinc pennies so for zinc try a latex eraser.
Admirable, trying to help, but just think...do you really think that eraser wouldn't leave scratches over the coin? Would you do that to a proof coin that had a spot?
no zink is cleaned by the materials in the eraser it works for all other pennies but works best in zink pennies