The Cum Zone originated from a soundcloud post in 2014, named "Voiceover Post MK 1 Origins", which has now unfortunately been deleted.
Dark Spider, the poster, paid a voiceover actor to read a list of his friends steam usernames.
It was reposted onto youtube, labelled "(ASMR) Welcome to the Cum Zone", this is where I originally found it in 2016
It was then adapted to the "Welcome to the Cum Zone [Official Video]" by OblivionFall After Dark in 2018
After then, it kinda exploded in popularity, and OblivionFall After Dark made the sequel, based on the second audio recording.
You can find more information on the knowyourmeme page (use an ad blocker, their site is garbage!)