Does the {ash zealot} work only on cards with flashback or does it work on stuff like {diabolic servitude} {breath of life} etc.
If it is cast from graveyard then yes, like if you cast {Gravecrawler} from the graveyard,
Well, something that's actually cast, for starters. So, for example, a spell with flashback like {Think Twice}. Or, a spell cast from your graveyard because you've resolved {Yawgmoth's Will} earlier in the turn.
That's pretty much it. If it isn't a spell being cast from your graveyard, then Ash Zealot won't do anything -- the card was basically made to interact with spells that naturally have flashback, as well as {Snapcaster Mage} (since it can give flashback to any instant or sorcery).
Cards that say return target card from graveyard aren't affected by Ash...
RESOLVED
Thank you