How to counter Protoss' fast expand as zerg?
Lately I have had trouble while playing Zerg defeating a Forge Fast Expander. The trouble is that I can't break his walls quickly or easily. I have tried searching for strategies online about breaking a FFE however no good results appeared. I did beat one by using a Nydus canal but the player wasn't quick enough to respond and surely could have defeated it if given a few extra seconds.
So what are some good strategies to defeating a Forge Fast Expander as Zerg?