Inside the cave, continue the only one path in there until you will reach to the small hole in the group, jump to the hole… An the things in the tittle will be appear that is lots of mob spawner (zombie spawner), and also you can find some chest in there, but careful will the zombie, you will got the following items: is irons and string. To get more zombie spawners continue straight ahead the cave.
Minecraft PE Seed: -1054196912 – Mob Spawners
In this seed you spawn in a large grass landscape biome. From the spawn to come to the large cave, just walk straight ahead until you see a small pool water, that is first sign you very close the cave, after a while you will reach to the entrance of the cave. Go inside it.
Seeds : -1054196912 Work in PE ver0.9.0+ or ver0.9.5