Thanks for aksing the query,
Chipping and breaking of the zirconia crown occurs when your biting forces are high.
I would suggest you to visit the Prosthodontist and look for a full ceramic or metal fused to ceramic crown, discuss with your Dentist
about the treatment options.
Zirconia crowns does not have any relation with your immune system so you can definately think of different treatment options.
Maintain a good oral hygiene
use antiseptic mouthwash rinses twice daily.
Hope this helps out.