If the Dragonborn has a high Sneak skill, it is possible to drop down without fighting the bandits by circling to the northwest side of the ruin, then dropping down towards the quest marker, on top of the roof above the door, then again to the door level (note that the last drop is long enough that it may cause injury). Once inside, there is a group of bandits on the way when following the quest marker. The last one has Maluril's key - if that is not obtained, then the lock to his room can be picked. It appears the bandits have killed all the Dwarven Spiders.
Maluril sits towards the back of the room with his side to the entrance. It is a dark room so it is possible to sneak for a back-stab, or to kill him with an arrow. Maluril's Journal is on the table at which he was sitting, and the Speech skill book A Dance in Fire, Book VII is on another table in the same room.
The Dragonborn should return to Nazir for the reward.
Fascinating race, the Dwemer. Powerful... and extinct. "Yes... quite. But if that power could be harnessed. Controlled. The possibilities would be... But... who exactly are you? And why are you in here? I think it best you leave Mzinchaleft. These ruins can be quite... dangerous."
The only thing you will discover in Mzinchaleft is death. "Death? Oh, there's death to be found here, to be sure. But not my own!"
(Remain silent) "Who are you? Why are you here? Leave this place. I have much work to conduct...."
Only the second option will turn him hostile, the other two will end the conversation. Upon returning to Nazir he will say, "I hope the elf didn't give you too much trouble. I once got set on fire by a sorcerer. Nasty business, that. But I digress. Here's your payment."
I must kill the wizard Maluril, who can be found investigating the Dwarven ruin of Mzinchaleft. I may use any means at my disposal. When I am done, I am to report back to Nazir at the Sanctuary and collect my reward.
Maluril is dead, and I have collected my reward from Nazir at the Sanctuary.