first a written test was taken (it was a 90 min online test , having four sections - verbal,quant,reasoning,data sufficiency ). the shortlisted candidates then had a GD session. After that followed a case study round. 30 min were given to prepare a solution for the case , followed by an interview based on it. (you dont need to solve it completely , what they seek is your approach which should be explained to them step by step.) then there was a behaviour interview that involved guess estimation questions. they ask you any random question , you hav to come up with a number , e.g. estimte the number of traffic lights in delhi or estimate the number of people coming to sign up if you open dance schools all over india. your solution must have some agreable logic behind it. Lastly , there was the principle or the hr interview. it is based mostly on your CV and some general HR questions like why should we hire you , why ZS , why consultancy etc.