For this I got My friend to train a group of zombies at the top of the castle between the death ray and the spiral tower with the painting. I took the wonder sphere , (its either the one at the death ray or one in the corner above double tap, i'll check tomorrow ) and shot while I was in the air. You'll get this easy enough after one or two goes of the wonder sphere
. It's a short journey through the air so just tap
quickly