A-skill for zephiel?

I'd go for atk +3. if you want more bulk you can go with +3 def.

Why dont you want to use death blow 3? It comes with him and its potent than +2 atk.

I went with Fortress Def 3 when he released since I got a Lukas directly when the banner came out.
But now I use Boeys Earth Boost 3 on him since he has the highest HP stat in the game right now and in general is pretty damn tanky.

If you aren't going to be using a pure tank skill like Earth Boost or Fortress Def I would reccomend going with Fury, you can use it to play a bit riskier with Reprisal/Vengeance + HP Seal if you want or just have a healer on your team to sustain the 6 HP cost.

I 5*'d Zephiel last week and left his A slot empty until a couple days ago when I slapped Earth Boost 3 on him when I summoned some Boeys. I also have ATK+2 inherited to him but not learned yet because I think it was a shoe in skill when I was giving him pivot from Cherche. I'd take the extra attack over extra defense until you can get something better.