Eswar’s thinking is correct. Although both are exothermic reactions, the type of chemical reactions is different.
Case (i) : When water is added to calcium oxide it forms calcium hydroxide. It is an example for combination reaction.
CaO(s) + H2O → Ca(OH)2(aq)
Case (ii) : When hydrochloric acid is added to zinc pieces it would liberate hydrogen gas which is an example for displacement reaction.
Zn(s) + HCl(aq) → ZnCl2(aq) + H2(g) ↑