Are those two directly at the palace, or elsewhere in the city?

They are in a slightly smaller wing to the side of the main palace.

How weaponizable are their surroundings? Any convenient hanging objects? How far are they from the nearest other guards?

There are some torches bracketed to the wall with steel, nothing else weaponizable nearby - except for the guards' weapons, theoretically. There is one guard stationed at the entrance to their wing and another pacing a corridor away from their doors.

He looks around for anything that could be knocked over to make a loud noise, and when he's finished searching the area he returns to his body.

There are some statues in a few of the hallways that could be noisily knocked over, probably. It's hard for the paperman to tell how securely they've been installed.

Good enough.  He makes some wind talismans, and a few more firestarting talismans, and a couple slicing talismans before he sneaks out of the house, through the same window he cut open last time.  He follows the route he found with only two guards, keeping an eye out for other people that weren't there when he looked with the paperman.

There's one extra guard who seems to have been roving around on some sort of patrol! He's approaching down the corridor around the corner from Wei Wuxian.

Is there a convenient corner or door for Wei Wuxian to hide behind.

There's one of those ugly stone statues he had noticed earlier, he could try that? He could also.... run all the way back down the hall in search of more corners? The only door on this hallway is locked.

He's going to try and hide behind the stone statue.

The guard is not paying very close attention; he passes him by without incident.

He continues walking towards Wen Zhuliu's room, continuing to keep an eye out for unexpected guards, stopping when he's just out of sight of the two guards he knew about.

No more unexpected guards appear. The two expected guards are chatting together in low voices.

He uses a wind talisman to knock over a statue and make noise down the hall away from him.

The guards make alarmed noises! They put their hands on their swords and hustle in the direction of the commotion. 

He slips through the door while their backs are towards him, and continues towards Wen Zhuliu's room.

He doesn't encounter further obstacles before he reaches Wen Zhuliu's door. 

He slips into Wen Zhuliu's room, and looks around to find Wen Zhuliu's sword.

The sword is sheathed and stowed under his pillow, the hilt just barely poking out.

He carefully draws the sword from the sheath, trying not to move the sheath or disturb the pillow.

He succeeds, but the metal makes a very soft noise as it unsheathes. Wen Zhuliu's face twitches minutely in sleep.

Well if Wen Zhuliu is faking his sleep he's about to find that out.  He lays the sword along Wen Zhuliu's throat and draws it across, slitting his throat.

Blood spills everywhere, thick and black in the dim light.

Wen Zhuliu's eyes open and flicker. He convulses, his hands twitch - the sword trembles in Wei Wuxian's hand, trying to answer the call of its master - and then both it and Wen Zhuliu's body fall still.

Good.  He returns the sword to it's sheath, and slips carefully back out of the room, taking the same path he took coming in, once again stopping when he is just out of sight of the guards.