When one is discussing the relative merits of filling and sealing materials, gutta percha is often compared to other materials.
In fact this is a canard.
In fact, gutta percha rarely comes into contact with tissue...if it is used properly.
If we are to make valid comparisons we have to find out what kind of sealer is used with gutta percha, because it is the sealer that contacts tissue, not the gutta percha which is usually well short of the apex.
In general ZOE when injected via a syringe CAN be, but not always IS less toxic than the ZOE that is used with gutta percha.
Here's the reasoning.
When ZOE is mixed thin it contains more free eugenol, that is, eugenol that does not combine with zinc oxide. This is necessary because it has to flow around the gutta percha to affect a seal.
ZOE injected with a syringe can be much thicker, depending on the quality of the syringe that injects it.