What is the chemical reaction when zinc is heated with caustic soda solution?

Zn does not reacts with water ...

Elementary zinc does not react with water molecules. The ion does form a protective, water insoluble zinc hydroxide (Zn(OH)2) layer with dissolved hydroxide ions, according to the following reaction mechanism:

Zn2+ + 2OH- ---> Zn(OH)2(s)

it only reacts with boiling water forming zinc hydroxide and hydrogen...

Zn + 2H2O ==> Zn(OH)2 + H2

Its fairly nonreactive.

Zn hardly reacts with cold water.

It does however react with steam (heated water) to produce zinc oxide and hydrogen gas:

Zn (s) + H2O (l) --> ZnO (s) + H2 (g)