Yes, several events overlap for the different timelines, such as the Purificator
and all, but the Zyainor you are refering to does not exist yet. And in the Human book Gardon won,
in the Orc Book he retreated so neither the Golden Guard ending nor the Ironfist ending of the SHB
have occured in this timeline as both end with one major character dying.
This is the current worldmap,
even if it is pretty... simple and missing several places. You only have to imagine Lor and Isalmur
being conquered by Demons. There also is no Quarantine Zone yet.
The Orc Book does not "revive" characters or anything, it is an alternate storyline. It is like that
for ALL different races, so neither choice of one race's campaign has any effect for the others.
Not even the same events occur, i. e. mind you that Merlon dies in the FOB and CAN die in the FUB
while in the SHB, following the FHB, he is still kicking that Thunderstorm.
By the way, if you want something crazy, I suggest changing the choices to a way that makes the
Orcs pretty much kill everything and then watch the Interlude following Chapter Ten again.
You will see why.
[(spoiler]