Welcome to Legends ZA OU! In this Pet Mod, we will have a speculative metagame based on the Pokemon and items currently usable in Pokemon Legends: Z-A, in a what-if on them being allowed in the turn-based battle mode. This Pet Mod will have minor changes, namely the new Mega Evolutions having proper abilities. Because this Pet Mod is based off of a Pokemon game, we will be using the personal data from Legends: Z-A for learnsets, stats, etc. with the exception of Mega Starmie. Terastallization will also be unusable. The final change is that every Pokemon will have its National Dex movesets on top of the moves they learn in Legends: Z-A; this is mainly because otherwise there would be every single entry hazard but zero hazard removal or Heavy-Duty Boots, and that is just not fun!
So basically it's regular turn-based battles only allowing Pokemon and items available in Legends Z-A (+heavy duty boots bc screw hazards apparently). The Pokémon have acess to their abilities and their NatDex movesets, but there is no terastalization, only Mega Evolution.
Since the megas have no confirmed abilities yet (aside form Starmie ig), the community has given them custom ones, and a list of the new abilities is present on the forum.
Legends Z-A OU forum