Spoiler: (highlight to view)
As many of you know, Looker lost his memory in OR/AS, Zinnia has experience with alternate dimensions, and Anabel was in a wormhole for a very long time. So, I think they all are connected and possibly chronologically connected due to hints in the game. I'll start by telling you that, according to Bulbapedia, trainers Red and Blue and Wally are 11 in Gen 1, and 31 in Sun and Moon, so we're working by that logic.
Now, I think it all begins with ORAS, which is technically the first game, chronologically, alongside Red/Blue and the remakes. Zinnia, presumably based on ingame text, lost her daughter in the non mega timeline and instead has Whismur, who is named after her daughter Astar, and they live in the mega timeline. Somehow Zinnia knows her daughter is in the non mega time line so Zinnia must have some experience, most likely forced experience, traveling through other dimensions at LEAST one time. In the end of OR/AS she leaves Hoenn to go somewhere unstated.
Looker, in OR/AS, has suffered a memory loss for an unstated reason. I am sure he went through a wormhole and that is why, and was in there long enough to lose his memory, but not long enough to have the aura on him that lures Ultra Beasts to him. 10 years later, during what I believe must be around X and Y timeframe, after the post game of XY, Looker has to go due to his job requiring him to travel. I believe this was to begin the Ultra Beast hunts. In Sun and Moon, Looker states that 10 years ago, he was working with Nanu to hunt Ultra Beasts, which would match up with XY. Perhaps Looker wasn't originally a detective and only became one AFTER he was found washed up on shore in OR/AS, the first chronological games. Perhaps he even became a detective in order to "Look" for his original identity. To find out who he is.
In Sun and Moon, Looker and Nanu tell you a person was found washed up on shore with no memory 10 years ago. I believe that person was Zinnia, and Looker was called to investigate her mysterious circumstances. After leaving Hoenn in ORAS, Zinnia had been taken into the Ultra Wormhole for possible years, enough time to lose her memory and carry the aura around her body that lures Ultra Beasts to her, just like what happened to Anabel. When Zinnia was healthy enough and able to, which may have taken months, she was allowed on the missions with Looker to find the Ultra Beasts, and subsequently killed by Guzzlord. Ten years later, we have Sun and Moon version with Looker haunted by his past and still trying to find himself.
Thanks to the 20 year gap between ORAS and the Gen 1 games all the way to Sun and Moon, and Looker telling us about what happened 10 years ago from Sun and Moon, we have a huge enough gap to theorize and connect some possibilities.