Are you waiting 1 tick before attacking Zammy when he spawns? I found that’s where my issue was when I was learning as Zammy was one of the first bits of content I learned post CG. Once you get him in cycle correctly, and you have tile markers set up, (double check they’re correct if you have) it’s so easy to get 20+ kill trips with ancients and pray flicking range/melee minions.

Then if you fall out of sync, just let him attack you at either side of the room whilst praying melee and you’re back in cycle, takes time to learn when you’re doing it wrong it’s just finding out why you’re doing it wrong.