The important thing is to make sure your zoroark understands that his worth both as a living being and as your partner are not determined by the battlefield. If you can reassure him that the way you see him hasn’t changed, despite the fact that he can no longer perform what had been one of his main duties on your team, life during and after recovery will be a lot easier for him. My advice would be to find something he can do that will keep him close to you as often as possible. Don’t keep him from watching battles if he wants to do that; rather, simply keep him from joining. Preventing him from watching will make him feel excluded from your life, especially if you battle frequently. Perhaps even allow him to mentor your krokorok and lucario if his condition allows him to use his abilities outside of the high-energy environment of the battlefield.
As for breaking the news to both him and the rest of your team, break it to your team first. Tell them that their teammate will need all their support but that just because he can’t battle doesn’t mean he should be treated as if he can’t do anything. Make sure they understand that he needs them to include him in as many of their activities as he can physically handle, and let them know that most likely, your zoroark won’t appreciate being treated gently. Do this in a confident but gentle tone, and speak clearly. Although the news may be devastating to them at worst (or perhaps disappointing at best), getting them to understand your zoroark’s condition as quickly as possible will help you to break the news to your zoroark.
Once you’re ready for Zoroark, inform him gently. Have his team in the room with you for support, and let him know that you and the others will work hard to help him through recovery.
Best of luck, anonymous.