I was just directed to this fanpost by smileyman at Niners Nation.  And well, if we're going to learn the 4-3 under, we might as well learn the ZBS too, right?  I'm not sure why they went through all the trouble considering Patrick Willis can singlehandedly destroy the zone blocking scheme with an indirect thought about it, but lets take advantage of the situation. For those of you who don't want to read, smileyman also directs us to a number of video clips that can help:  

Brian Billick explains zone blocking 

This is just a quick run through; it doesn't give you a lot about the actual linemen, but it does tell you why vision is so important for a Zone RB.  

The White Board

Part 1

Part 2

Part 3

This series is a high school coach explaining the ZBS to his players.  First on the board, and then on the field.  Grainy videos, but pretty in-depth.

Z Report

And if you want it from Mr. Z himself, I'm sure this video made the rounds awhile ago, but I wasn't really paying attention when it did.  Kailee Wong and Lance go over the blocking scheme on the whiteboard as well.