First off, The manual for your bike is available on the home page and you have to be logged in to see it. It's the
ZN1300 Service Manual.
You also need to download the KZ1300 Service Manual because a lot of the basic information for a lot of the mechanicals are found in that manual
Now, your issue-
I think the first thing you need to confirm is that the engine is not seized. It's been sitting for 20 years and it's possible that one or more than one set of piston rings has seized to the cylinder walls. You need to remove the right engine side cover and try to turn the crank over with a wrench in a clockwise direction. If it's free to turn good. if not then you need to free up the rings. I'm sure you could ask 5 mechanics how to do this and you'll get 5 different answers. My point is to confirm that the engine is free first.
If it is free, then the next thing to confirm is that the starter is working. You can do this by using a jumper wire ( ideally a booster cable) and run it from the positive terminal of the battery to the heavy wire on the starter relay (it should be a heavy black wire) By doing this you bypass the starter relay, ignition switch, engine stop switch etc. All this does is confirm the starter motor is not seized and functioning.
The clicking noise you hear is the starter solenoid and it could be clicking if the battery voltage is low or it might be that the solenoid is energizing but the contact in the solenoid are not making contact allowing battery voltage to flow to the starter motor.
That should get you started in the right direction.
As far as your DFI code as per the chart I got from the Zn1300 Manual what the DFI is telling you is that there is no pulse signal coming from the engine and of course there's not. The engine is not turning over so don't worry about that at the moment.