Nec nd-3520 Z-CLV?

Nec nd-3520 burn dvd±r at 8x and 12x with z-clv ? I look the test in preview of nec nd-3520a with fw1.04 and fw ld beta 3 and look z-clv at these speeds.

NEC drives use a mixture of CLV Z-CLV and CAV to burn media.
6 - 12X Z-CLV
13X - 16X CAV

The pioneer dvr-109 uses the same mixture ?

Does 6x Z-CLV offers the best writing quality on burning dvds?