I tested the damage difference between a normal build on Zoe and this build. In a 1v1 Zoe is a tiny bit weaker than with a normal build, but in a teamfight she deals more damage, because the imperal mendate mark deals so much damage.
Together with Rylai's you don't even have to hit an E to get this damage off.
Seraph's is there to help with Mana issues.

Now, if you look at the prices of the items, you notice that this build is pretty cheap. As a support you won't gain as much gold as the other roles and a cheaper build fits perfectly with that.

When I tried out this build for the first time, I went 8/2/16, so I would say it's pretty good.

You basically play with this build as if you would play normal Zoe support.

Poke with Q, try to get E's down and proc electrocute. Try to stop the enemy from farming and avoid getting hit by stuns etc. or otherwise you are probably dead.

Oh and an adc who can dodge some skillshots also comes in handy, since you can't heal or shield.

Tip if you are playing vs. engage support: If the support engages on your adc (or you and you're not getting hit), just E the enemy adc and he will sleep half the fight :)