In a certain code language, 'He is my nephew' is coded as 'Co Pv Zs Mn', 'That is my car' is coded as 'Zs Pt Pv Ga', 'He is your uncle' is coded as 'Co Pv Ex Yz'. What is the code for 'nephew' in this code language? 

Mn

In all the above statements, 'is' is common.

Thus, it can be deduced that the code for 'is' is 'Pv'

From first and third statements, 'He' is also common,

The code of 'He' is 'Co'

From second and first statements, 'my' is codded as 'Zs'

Thus, the code of 'nephew' is 'Mn'.