You Beat the main game, and since you said "All TMS in legends Za" Including with the dlc.
-Walking Around looking for the Yellow Glowing PokeBalls laying around.
-Beating the mainline Fights, using Canari as a E.g.
-Doing Mables Tasks and check if you have the shiny charm (Since its the last reasearch task)
-And there are a decent amount of side quests giving you TMs
May Contain Spoilers for Dlc
I have the dlc but I'm only on Research survey #2 after the Rouge Absol Z fight and of the top of my head, I dont believe I have gotten any TMs but I could be wrong.
**I would Start with Mable and Walking around.**
Like the comments said there are bewteen 100-125 Total TMs in-game.
Hope This helped. (Im Prob missing something).
EDIT: I did a little more research and I looked on Serebii and I found this. https://www.serebii.net/legendsz-a/tm.shtml It is a link to Serebii and has lists and locations.