In the given chemical equation: Zn + 2H^+ → Zn^2+ + H2
The substance being oxidized is zinc (Zn).
During the reaction, zinc loses two electrons (oxidation) and is converted into zinc ions with a charge of +2 (Zn^2+). This process involves the transfer of electrons from the zinc atoms to the hydrogen ions (H^+), leading to the formation of hydrogen gas (H2) as a product.