Zinc is often used as a safe, stable, and dirt-cheap reducing agent for inorganic and preparative chemistry. For example, the easiest way to produce chromium(II) and vanadium(II) solutions is reduction of higher oxidation states with a mixture of zinc and hydrochloric acid. However, zinc can also function as an oxidizing agent. Stronger reducing agents such as magnesium and possibly aluminium are capable of reducing zinc(II) ion solution to solid zinc.
A couple of years ago, I dissolved chopped up pennies in vinegar to form zinc acetate. After several weeks, strong-smelling and damp crystals had separated out of the solution. I placed them in a container and never used them until recently. Then, I took some of these crystals, dissolved them in water, and placed the entire magnesium firestarter rod in them. Some gentle fizzing was observed, which is normal with metal salt-magnesium reactions. Then, a blue-gray film was beginning to form on the magnesium. I checked 12 hours later and noticed the piece of magnesium covered with crumbly growths of zinc. They were not spongy or metallic, and dried to a powder. After another day of drying, they were covered with a white hydroxide film because of their finely divided state. I photographed them in this state and then disposed of them.