How can I approximate this transfer function?

[gaus12777]

I don`t know how can I approximate this transfer function

into this

In my book, pole is close to imaginary axis, so It can be approximated.

 

[boneh3ad]

Is that not just an assumption of having zero damping? If the pole is near the imaginary axis, the means the system would very nearly be purely oscillatory with no damping and you could just remove the $\zeta$ term to get an approximate answer. Unless I am missing something here...