If you "just" lay a rock that has Zos on it, on another piece of LR...
Eventually, the zo colony will "multiply" and spread on to the other rock...
I had a "finger" sized/shaped piece with zos on it that I placed in a crevise of two rocks...a couple (6-8) weeks later I can not move the finger shaped rock cause the zos spread on both sides and "grew" the rock in place...
If you don't want to "wait" for haphazzard growth patterns you can look into "fragging" zos on to your "display rock"
I believe Kip has been working on a multi-colored piece...