Given here is that the absolute value of Av is zero, which leads, as far as I understand, to a short circuit on Zout and Yin.

Required is Vout. As far as I understand there are two equations, first:

Vout,n = Iout * Zl

Second:

Iout(Zg+R1+R2+Zl) = Vg-Vn,1 + Vn,2

and we are supposed to substitute the second eq. in the first to solve for Vout.

However, the solution had another way of describing Vout which is:

Vout = -IR2 + Vn,2

Can some one explain this misunderstanding?