User blog comment:AnonymousAK/Demon's Royale/@comment-25121709-20140715151833/@comment-24066070-20140716073547

For the sake of having Zoldeo fight at the top of his power, it would be better for that "funny deity" to use the Zoldeo from before he broke the taboo. It would be valid since Zoldeo learned Human Subordination from Precht and Precht wouldn't teach him before he joined the SKoP, so that Zoldeo certainly counts as a member of the SKoP.

This Zoldeo would be more versatile than the one merged with the Spirit.

For starters he has the actual Key to summon Capricorn, thus having a Spirit who can serve as a decoy/bodyguard while Zoldeo unleashes his magic. Secondly, he may still have the time to use Huma Raise after taking a serious blow. When he is merged, a serious blow forces him out of the host body and it's game over for him.

I'm not sure if Zoldeo can use Huma Raise to forcefully merge with a Demon, I believe he said he merges with the target if it isn't human. This includes Spirits, but since Demons aren't human either it could work on them as well. If he, for example, sets his mind on merging with Silver, he would have a better chance of pulling it off when the actual Spirit Capricorn distracts Silver.