how well does watch os 4.3 run on series zero

Faster in many places, more battery (something like 20% increase). Don't take my word for it, you can find a lot of feedback same as mine on posts on reddit and all around. 🙂

I updated Saturday and can only getaround 4 hours from the battery on mine. Uninstalled all apps, even turned off back ground refresh on watch. Be weary of the update.