separating hyperplane theorem proof

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I need help understanding the last part of this proof, the lemma they are refering too is just a lemma about convex sets that shows us that p is unique:

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I do not see how H* separates C and z.

The equation for H* is:

$(z-p)^Tx=\frac{(z-p)^T(z+p)}{2}=\frac{|z|^2-|p|^2}{2}$

And the elements in C sattisfies:

$(z-p)^Tx \le (z-p)^Tp$.

Now from what I understand in order for it to strongly separate we must have.

$(z-p)^Tp < \frac{|z|^2-|p|^2}{2}<(z-p)^Tz$.

Is it correct that this is what we must have? Is this inequality obvious?