Bad voltage regulator/rectifier?

If the main fuse is good, and you've got voltage at the starter relay input terminals, then you've got to look at the out voltage output of the starter relay and the headlight relay. If the starter relay is toast, then you won't get any power to the reg/rec, headlight relay, anything. Also look for splices in that line. If you see any don't mess around; just redo them.

That would only affect the charging system and should cause it to not turn over.

If you have power at the starter... check the trigger wire to the solenoid. If you're not getting the 12v trigger stab, then it has to be a safety or the start button itself.

I believe Paul said he replaced the starter relay, so the next likely candidates are the starter button, corroded starter motor connections, or, as you said, a wiring fault in the harness.

Recheck the wiring harness for dodgy connections, (pull every single connector apart and clean them) then look for any spots that appear as if they could have been pinched by the seat, tank, triple trees, or over tightened zip-ties (common problem areas).

Side stand switches come in two basic varieties. Some will prevent the bike from starting, some will kill the motor as soon as you put it in gear. Either way, disconnect that stupid shit. Usually, all you have to do is bridge the two switch wires together.

JC

Tipover sensor? lol

On the ZX-11?
The tip over sensor is the riders ankle, the back up being the shoulder.
Tip over sensors are for fancy bikes with "lectronic ciruit mobbies"
To reset the sensor, you simply placed the bike back on two wheels

Innards of the ZX are vacuum tubes linked to brass steam work logic engines powered by rain water.

On a couple of my bikes, you had to take off the seat and reset the switch manually.

Doesn't sound like it, but are you still getting the "click from the starter box" you mentioned earlier?

When the ZX was working properly did any lights turn on when you only turned the key? On my bike (old R6) the dash, headlights, taillights, and other shit all come on when I turn the key, regardless of what is happening with the kickstand, killswitch, starter button, or being in gear. From my recollection all the bikes I have been around do "something" when you turn the key on. If the ZX did anything when you turned the key before, but isn't anymore, you may want to investigate your key switch.

Prior to this, with the old battery I'd get juice (lights..the clicks etc ), but it wouldn't start.

Pulled off all the bodywork to do cleaning and checking.
Got the new battery, tossed it in.
Zilch..no lights, no nothing.

With switch off
test the battery -12.x
Positive terminal on battery to frame - 12.x
Connections on the starter relay - 12.x

Turn key to on
test the battery - shoots down to zero
Connections on the starter relay - shoots down to zero

Did you charge the battery at all before you put it in?

You can hook the old battery back up and see if it does the same thing (nothing and voltage dropping to zero) or you can connect jumper cables off a car (with the car off) to your new battery and see if the lights etc. come on. If the same thing happens it may be a short in your ignition. If it acts normally the battery may have been shipped without a charge or it is a bad battery.