Let \( z \) be a complex number such that the real part of \( \dfrac{z-2i}{z+2i} \) is zero. Then, the maximum value of \( \lvert z - (6 + 8i) \rvert \) is equal to
\( 12 \)
\( 8 \)
\( \infty \)
\( 10 \)
