Why does Q not correspond to (1+i)z2, given that you have already accepted that P corresponds to (1+i)z1, accordingt to i)?

It seems to me that you are getting P by rotating A around 0 by +90 degrees, whereas you are getting Q by rotating B around 0 by -90 degrees. Which is right: rotating by +90 or rotating by -90 degrees?

Since M is mid point of QP, then QM = 1/2 (p-q)

=1/2 (z1(1+i)-z2(1-i))

...

=1/2(z1-z2) + i/2 (z1+ z2)

But QM = M - z2

z2 + QM = M

therefore,

M = 1/2 ((z1+z2) + i(z1 + z2))

However solutions has 1/2(z1+z2 + i(z1-z2))

Thanks in advance.