How can I debug a series of piped commands in zsh? The command 

ioreg -lw0 | grep \"EDID\" | sed "/[^&lt;]*&lt;/s///" | xxd -p -r | strings -6


is not giving any result. Can any one help.

I got this command from an article that maintains (I paraphrase) that rMBP can have Samsung / LG screens,  and that the LG screens are all defective.

My MacBook Pro retina 13" so I naturally wanted to check the details of my hardware. Mine is zsh
One way to debug command-line pipes is to insert | tee debug.txt between two steps and look at the file debug.txt to check whether the previous steps are correct.