@Override
    public void multByZ(long[] output, long[] in) {
      Field25519.mult(output, in, z);
    }
Creates a cached XYZT

@param yPlusX Y + X
@param yMinusX Y - X
@param z Z
@param t2d 2d * (XY/Z)
java_src/src/main/java/com/google/crypto/tink/internal/Ed25519.java