Voxel Marching Hibrid

I need help with optimizing a voxel based game i am makeing, the part that needs refinded is a function that goes thought every block in a chunk and checks a 5/5/5 area around it, it does this for every shape and rotation i make. this makes a marching cubes like terrain, but is still cube based, and will break like blocks, think of the game space enggers in it's blockbuilding, mixed with voxel based minecraft.

So what i need it to figure out a way to compare 1 5/5/5 arangment of blocks extreamly quick.

takes more then 20 seconds for this chunk, and i need it much lower for my game, so post any ideas please.