Yup, call, DO NOT EMAIL, Marzocchi....
with your question. Marzocchi is great at making forks that have interchangeable parts. They are one of the few that actually do this. Makes sense as it keeps production costs down. But, there are some things that just can't be retro fit to other forks. I'm not sure about your instance as I don't know what fork (for certain) you are trying to add the lock out to. There are two types, the ETA and ECC systems. Both do pretty much the same thing, but are not true lock outs, more like "lock downs". When they are activated they lock the fork down about half way into their travel. Nice for climbing as it changes the weight bias of the bike forward and makes it easier to keep the front end down on the climbs. Anyway, give Zocch a call and tell them exactly what you want to do. Be armed with the exact model of your fork. They'll tell you honestly if you can do it. Just make sure that they hand you off to the tech department. Those are the guys that will know for sure.
Good Dirt