Two amphoteric oxides that react with acid and base are:

The metallic oxides that can react with acids and bases are known as amphoteric oxides. These compounds behave as bases when they react with acids and form normal salts.

These salts also behave as acids when they react with specific bases and form a complex salt as they cannot replace the metallic ion of the base.

ZnO and Al₂O₃ are known as amphoteric oxides as thy react with acids and bases both to form salts.

$$\begin{gathered} \mathrm{ZnO}+2\mathrm{HCl}\to {\mathrm{ZnCl}}_2+{\mathrm{H}}_2\mathrm{O} (\mathrm{Reaction} \mathrm{with} \mathrm{acid}) \\ {\mathrm{Al}}_2{\mathrm{O}}_3+6\mathrm{HCl}\to 2{\mathrm{AlCl}}_3+3{\mathrm{H}}_2\mathrm{O} (\mathrm{Reaction} \mathrm{with} \mathrm{acid}) \\ {\mathrm{Al}}_2{\mathrm{O}}_3+2\mathrm{NaOH}\to 2{\mathrm{NaAlO}}_2+{\mathrm{H}}_2\mathrm{O} (\mathrm{Reaction} \mathrm{with} \mathrm{base}) \\ 2\mathrm{ZnO}+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{ZnO}}_2+{\mathrm{H}}_2\mathrm{O} (\mathrm{Reaction} \mathrm{with} \mathrm{base}) \end{gathered}$$                                                                                      

 Here NaAlO₂ and Na₂ZnO₂ are complex salts because aluminium and zinc being less reactive than sodium, cannot replace sodium from the base. Hence, they combine with sodium to form complex salts called sodium aluminate and sodium zincate respectively.