f-related vector fields

Let M and N be manifolds and let f:MN be a smooth map. A vector field X on M and a vector field Y on N are said to be f-related if

dfp(Xp)=Yf(p),pM.

This means that for every function

h:NRXp[hf]=Yf(p)h.

Suppose that X is f-related to Z and Y is f-related to W. Show that [X,Y] is f-related to [Z,W].