I started playing and didn't think I was going to play for so long. I really had fun playing this. Sometimes my zombies would get stuck because there was a zombie in between them so they couldn't merge. I just had to select that one and move it but, found out I could make them all merge together. They would then separate on their own leaving a bunch of 100 level/HP zombies behind.
I had a huge horde and attacked a castle and fort at the same time and froze my game. I should take it slow next time. I don't know what I would suggest to improve and I didn't see anything to call out as an issue. This hit a spot with me and I like it.