The Cathedral is the best place - I'm not even sure I've seen that many chandeliers outside of that zone. Additionally, the zombies in the Cathedral seem to want to linger under the chandeliers for extended periods of time. In some cases people have helpfully died/been murdered under the chandelier drop zone, which means the zombies will just pig out and watch you pull the chain.
The easiest way to get there is to change your current quest Act 1, Quest 4: Reign of the Black King. Travel to the Cathedral Garden waypoint, and enter Leoric's Passage.
Alternatively, you could go to "The Legacy of Cain," quest stage "Explore Cellar" - play the quest until you get to the checkpoint at the Cathedral. Every time I've been to this level, there's been a chandelier with 4 zombies (2 that die when you drop it, and two who have a sliver of life left) right by the entrance:
The checkpoint means that you can just leave and reenter the game to respawn this group and the chandelier.
Strategy wise, you'll probably want to work alone, and leave any followers/pets/etc out of the equation.
Damage wise I haven't done calculations, but typically on Normal I can kill or do 90+% damage to most enemies with a chandelier hit. On Nightmare, they take more like 50%, if that.
Skill wise, I'd suggest:
- A weak, preferably ranged, AoE spell to soften them up but not kill them, and so you can be standing by the chain once you aggro them
- Movement abilities of some description, as you're going to be doing quite a bit of running (if you're not using the Cathedral checkpoint method)
There's not a whole lot else you could need - you want the chandelier to do most of the work, and these enemies are so weak there's really little to no threat to you, regardless of level.