Zabuza vs Nagato: Shinra Tensei renders silent killing useless. Nagato wins.
Zabuza vs Konan: Zabuza uses hidden mist jutsu and uses silent killing to kill Konan.
Zabuza vs Itachi: Zabuza can't get past Susanoo. Itachi wins.
Zabuza vs Kisame: Zabuza has the superior sword and better jutsu...