Unexpected behaviour with Coefficient

If I run

expr = (CF G[0, zb])/(1 - zb) + (CF zb^2 G[0, zb])/(1 - zb) + (2 CF G[1, zb])/(1 - zb) + (2 CF zb^2 G[1, zb])/(1 - zb); Coefficient[expr, zb, -1]  

in Mathematica 12.1, it returns

-((CF G[0, zb])/(-1 + zb)) - (2 CF G[1, zb])/(-1 + zb) 

Shouldn’t it return 0 since there are no terms in the form 1/zb in expr ?