On an argand diagram A, B, C and D represent z1, z2, z3 and z4 respectively.
i) Show that if z1-z2+z3-z4=0, then ABCD is a parallelogram
ii) Show that z1 + iz2 - z3 -iz4 = 0, then ABCD is a square.
Can I have reasoning behind all steps please? THanks