I have not looked at the format of the microcode yet, so this is only based on the blog post and discussions. K8 and K10 were based on Risc86 just like Zen seems to be. There also are some parallels, especially when it comes to sequence words and branch delay slots. There are also major differences like moving from triads to quads. I assume there are quite some similarities, but the current authors are better qualified to answer this at this point.