I made an offer to Rugan to sell Chest and divide the profit.
Then you have the Chest and also Rugan gives you Code word for entering Zhent Hideout safely.
BUT ... when you arrive down ther you see Rugan interogated and Olly allready dead. Zarys will Talk to Rugan and a History Check can provide you with a hint.
If failed History Check, you can try Persuasion Option to silvertongue Zarys.
Then you can kill Rugan as a sign of trust.
Zarys will tell you to bring chest to Baldurs Gate and you have the better Items at Merchant here.
BUT it seems theres a Bug even when this happens and often the Guards in Hideout start to get hostile even when declared to help the Zhents and got the Mission to Baldurs Gate.
ITS ALLWAS BREM WHO WANTS TO BRING JUSTICE FOR THE KILLING OF RUGAN...WTF hes really a friend of Rugan it seems. Attacking us even when his Boss Zarys ordered us to. Else we wont be part of the Zenths.
Or for future Release, never enter Zhent Hideout and bring Chest with you to Baldrus Gate for selling personally. But then it might be that Zhents will do a bounty on you in Baldurs Gate and Hunt you down.