Lenny mentions Zep alot in interviews as being big influences. Here's a good quote I found of him:
"When I first heard rock music this whole new world opened up to me.
"I got into Jimi Hendrix, Cream, the Who and all those great English bands like Led Zeppelin while smoking pot with my friends.
"Later, when I was on tour, Robert Plant actually opened for me. I was being a complete perfectionist pain in the a***, whereas he was so humble and sweet. I was taking things too seriously and being far too intense and in the end he just said to me, “What the f*** is wrong with you? Just loosen up,” and so I did."