I don't think it's possible, for a couple of reasons:

1) I don't think innocent summoners can learn Zodiac. You have to lower the faith gradually using Solution. I remember trying innocent in a battle with Elidibs only to have it miss completely.

2) It's unlikely that a random enemy summoner could learn Zodiac from your party any more than Zodiac cast on a friendly summoner. Blue magic/E-skills (which Zodiac is in essense) are transferable from monsters to heros, not in any other direction.