Time management is very much important in IIT JAM. The eduncle test series for IIT JAM Mathematical Statistics helped me a lot in this portion. I am very thankful to the test series I bought from eduncle.
Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Shashi ranjan sinha
As asked in your first question, there seems no easy or short technique for such calculations. Either the numbers involved in it will be given to be easier for calculations or you have to face such lengthy computations. For the second question, yes there is sign mistake in z¹.