My Zehir turned out to be quite weak. Without abusing the exile ability, I lost my army quite significantly. In the end, I had 30 Titans and 10 Goblins left, and that was it. But Fedya's Zehir was different. His troops wiped out the enemy instantly when his defense and attack were higher than the enemy's Lord, and his ranged units with Stone Skin had a defense of 126...
Maybe Zehir should be built as an Armageddon-focused hero, because with an attack of 12 and a defense of 17, he's not much of a fighter.
Did you give him any combat skills? Just magic skills? Mine also passed through in a similar way, and he wasn't very effective.