So my arc-mage recently joined dark brotherhood and he want to kill people without incurring bounty or raising his murder stat. So he killed that skooma dealer outside of imperial city and enchant these four items.

-Accursed Hood of The Mute: Silence
-Accursed Shirt of Dark Fire: Fire Damage
-Accursed Pants of Black Ice: Frost Damage
-Accursed Wrist of The Tortured (From tutorial): Lightning Damage

But he must wait for the victims to sleep and be tortured in his nightmare. So what are the actions to make those NPCs to equip those items so that I can send their lucky souls to Sithis faster?

Also, Is there any other zero weight items that I can enchant?

I think they automatically equip the best (most valuable) item in their inventory. So if you reverse pickpocket them it should work and they should equip it when they wake up.

Beside of what you have there are not so many more zero-weight items. I know there is one more pair of wrist irons in Shivering Isles.

I have only used a zero weight hood of damage (shock, I think). I would reverse pickpocket it of course, normally as the victim slept. The victim would wake up, equip the hood and, after a time, die. Even those with potions or healing spells would soon run out of juice and die as well.

I believe the 'getting up' after sleeping helped trigger them to don the hood. I also understand that in selecting what to equip, they consider both value (enchanted is valuable) of the item and where (alphabetically) it fits in their inventory. It seems you already named your items to alphabetically be at the top of the list.

There is one other quirk to watch out for. If the cursed item is considered armor, then it is subject to the "armor unequipped" flag on their AI package following sleep. If they're not supposed to be wearing armor, then they won't wear a cursed item that's armor. Conversely, they may choose an armor item over a piece of cursed clothing if the flag is set the other way.

It's funny, but I can't bring myself to break immersion with that trick. I just can't get my head around how you could slip a pair of pants into somebody's pocket when they weren't looking!

Not to mention that they'll wear some suspicious iron wrist. But to me it's just like another cursed items, you'll feel the need to wear it. I can use poisoned apples but I want to see those people suffer, not stand around and then suddenly drop dead. Watching their body scorched in flames, frozen like ice or electrified is sooo exciting. I can't get enough with this.

From what I've heard about curse items, the NPC might be more easily able to equip it if you put a bunch of AAAA's in front of the name such as AAAHood of Doom.

If an NPC is going to don a hood, he will grab the first one in his inventory (alphabetically). So having AAA precede the name of a cursed hood simply helps ensure that he will consider it before other like items in his inventory.

Unless he has the dreaded AAAAA_Magic_Hat_With_Feather in there...