An other hint would be;
If you are looking for Zin’rokh, Destroyer of Worlds consider not solving any Troll project before 450. Dig as many Troll dig sites as you can but level from 100 to 450 by using all the other races. I am not sure if it goes slower then using Troll during leveling and not saving them. I guess is the same more or less but you don't waste them on common items during the period when you can't uncover Zin’rokh, Destroyer of Worlds anyway.
my guess is that the "find rate" is so low because you do waste about 20 projects on the way to 450 also.
have fun and buy chocolate for your younger brothers. It does help.