Minecraft wiki entry for effect, associated text: To grant a Resistance V effect to the current entity for 1 million seconds, hiding particles: effect give @s minecraft:resistance 1000000 4 true‌[Java Edition only] or effect @s resistance 1000000 4 true‌[Bedrock Edition only]
To grant a Speed II effect to the nearest player for 60 seconds: effect give @p minecraft:speed 60 1‌[Java Edition only] or effect @p speed 60 1‌[Bedrock Edition only]
To grant a Speed III effect to the nearest player for 60 seconds: effect give @p minecraft:speed 60 2‌[Java Edition only] or effect @p speed 60 2‌[Bedrock Edition only]
To clear any Haste effects from all players: effect clear @a minecraft:haste‌[Java Edition only] or effect @a haste 0‌[Bedrock Edition only]
To clear all effects from all zombies: effect clear @e[type=zombie]‌[Java Edition only] or effect @e[type=zombie] clear‌[Bedrock Edition only]