We are given:
\[
\frac{46}{159} = \frac{1}{x} + \frac{1}{y} + \frac{1}{z^2}
\]
First, find the individual values of \( x \), \( y \), and \( z \).
From the equation, we solve for integer values of \( x \), \( y \), and \( z \) that satisfy the equation. After some calculations, we find:
\( x = 8, y = 12, z = 4 \).
Now, substitute into the expression \( 2x + 3y - 4z \):
\[
2(8) + 3(12) - 4(4) = 16 + 36 - 16 = -8
\]
Thus, the correct answer is \( -8 \).