(Sigh.) Does this really need to be spelled out?
(Sigh) It probably shouldn't, but I'll do it for you anyway.
The tech manual is not canon, just like print fiction in general is not.
There was nothing in The Trouble with Tribble to indicate that the Organians ever created a Neutral Zone between the Federation and the Empire.
There is a treaty in the Franz Joseph TECHNICAL MANUAL describing the zone ("750 parsecs in width").
Picard stated that the Federation in the 24th centruy was spread across 8,000
light years, The FJ tech manual shows the Federation in the 23rd century as a disc of unknown thickness, that's nearly 31,000
light years across. And that both the Romulan and the Klingon NZs are over 2,400 light years wide.
Condition 2: No armed hostilities may take place place between the Klingon Empire and the United Federation of Planets.
Don't get me wrong, I actually love FJ's tech manual, but it is just a piece of print fiction.