Op-Amp's Dominant-Pole Compensation
I agree with you that the wording sometimes is a bit misleading. 

(1) "...it is written that if Zo &lt;&lt; Zf the closed loop transfer function is easy to calculate because the loading capacitance IS enclosed in the feedbackloop."

That means: Because CL is considered as part of the feedback loop - and is, therefore, part of the time constant that contains Zo - the CALCULATION will be easy and CL will have no influence while letting Zo&lt;&lt; Zf. 

(2) As far as your last sentence is concerned: The author just states that for Zo &lt;&lt; Zf the resulting transfer function is identical to the the function already derived earlier for ideal conditions. That´s all!