https://bulbapedia.bulbagarden.net/wiki/Plasma_Fists_(move)
Copy pasting from the Bulbapedia wiki (which is a pretty standard place to go for these sorts of things):
Plasma Fists inflicts damage. In the remainder of the current turn,
all Normal-type moves will become Electric-type, including status
moves. This includes Max Moves, which will turn into Max Lightning (or
G-Max Volt Crash or G-Max Stun Shock for Gigantamax Pikachu and
Gigantamax Toxtricity, respectively).
The type-changing effect is applied after move type-changing
Abilities, so cannot affect an originally Normal-type move used by a
Pokémon with Pixilate but can affect an originally Fairy-type move
used by a Pokémon with Normalize.
Plasma Fists does not exist in the game data of Pokémon Sun and Moon.
As a result, a Pokémon knowing Plasma Fists cannot be traded from
Pokémon Ultra Sun and Ultra Moon to Sun and Moon, and if a Pokémon in
Pokémon Bank knows the move it cannot be withdrawn in Pokémon Sun and
Moon. In order to be transferred to Pokémon Sun and Moon, the Pokémon
(excluding Zeraora which has no data in Pokémon Sun and Moon) must
forget Plasma Fists.
All Pokemon on the field are affected, both allies and enemies, both in Singles and in Doubles, for the remainder of the turn (and more than likely Zeraora will move first with its' 143 Speed, unless Trick Room is active, in which case the move probably won't be affecting any Normal moves at it'll go last).
For both Gen 7 and Gen 8, it appears to operate the same, only that it effects Max and G-Max moves in Gen 8 (doesn't mention whether or not it affects Z moves).