You are usign ribner compensation technique, in general it is said that compensating by this method is quite difficult, The original paper by Ribner is "Design techniques for cascode CMOS opamps with improved PSRR and common mode input range". in general we try to decrease the capacitance by merging cascode devices S and D, as in this technique we are connecting a capacitor so we have to have a contact which increases capacitance.
In this paper with simple mos model, transfer function shows it is a 3rd order. so it makes life difficult with this technique to design. but it's a very clever technique.
Added after 1 minutes:
The paper which i mentioned does the work for designing. Hope this helps.