By zyme, I assume you are talking about a product like hygrozyme. I've read where some people use it every watering/rez re-fill. I only use it if I think I have a root problem, or when starting a new container using recycled medium.
Silica, I use it everyother watering and only through veg, and 1/2way through the stretch of early flower. Others use it all the time. I found no difference between all the time and the method I now use.