And does unequipping reset the count?
Thanky

Christmas fiasco ep1 on normal (500/600 kills in 10-15 minutes). Note that certain IDs offers some cool drops (like amplifiers or s-part)
You can run the same quest under ep4 or max attack, if you're after Photon crystals (less efficient but PCs).
There is an other quest i don't remember the name under ep4, it has a LOT of mobs but no loot.

The kill count do not reset if you unequip the item. It may display 0 sometimes, but dropping the item and picking it again to have it at the bottom of your list should solve this issue.

Thanks for such a detailed answer.

I would recommend EP1 party quest "Wrath of Forest" (not available in solo).

First room of enemies in Forest 1 is 4 waves of a total of 60 enemies: 15 [Rag] Rappies, 15 Boomas, 15 Goboomas, and 15 Gigoboomas in that order. Leave quest and repeat. Tedious but I found it quick with the command to go straight back to lobby.