Help needed - pleasehelp!! :)

By the Binomial Theorem, the constant term is $\dbinom{9}{3} \cdot 2^6 \cdot (-1)^3 = -5376$

A general term in the expansion is $\begin{pmatrix} 9\\ n \end{pmatrix} (2z)^nz^{-(\frac{9-n}{2})}(-1)^{9-n}$

The constant term means the z terms don't appear, which means we must have $n-\frac{9-n}{2}=0$  or n = 3

So the constant is given by $\begin{pmatrix} 9\\ 3 \end{pmatrix}2^3(-1)^6=672$