Zverev announced the possibility of not playing at all this season a few weeks ago and it seems likely after he pulled out of Seoul and Tokyo.
Zverev was initially expected to play for Germany in the Davis Cup but a recent setback in his recovery process made that impossible. Zverev announced he has a bone oedema that makes it very painful for him to do any kind of activity let alone play tennis:
"I have a bone oedema issue which causes me quite a lot of pain. I don’t know if it happened yesterday or not but yesterday in practice with Oscar [Otte] it got to the point where I couldn’t run or walk anymore."
He admitted in that interview that he'll see if he'll play this year but it's unlikely as he just pulled out of the Tokyo event as well as the Seoul event. The German did not release any statement on the decision to pull out but considering the complicated nature of the injury, it's unlikely he'll rush.
Especially not with the Australian Open so close to the start of the season. He's more likely to take the time off and heal fully.