If you need to perform repairs on your Kawasaki ZZR 1400 then it is always recommended to have access to a Workshop Manual to use as a reference if you need to know tips to take off a certain part for example Door and install it again properly.
Kawasaki ZZR 1400 Workshop Manuals will give detailed diagnostic guides for the vehicle so if something is wrong it will help you work out what the issue is and tips to repair it. Then you are able to assess if this can be done by yourself or in case the job is just too big you could make a booking for your ZZR 1400 in with a nearby friendly mechanic.
Kawasaki ZZR 1400 manual