Question

Zinc displaces Hydrogen from dilute hcl but hydrogen gas is not evolved with dilute nitric acid. Why?

Answer 1

This is so because hydrogen combines oxygen to form water.
Here is the balanced equation for the reaction:
Zn + 4HNO$Zn + 4HNO _3 gives\\ Zn(NO _{3} ) _{2} + 2NO _2 +2H _2O$O

Answer 2

it cannot displace hydrogen when reacting with dilute HCl.