i only want to zoom like a optifine zoom that all it can doHi there, if you mean to change the FOV of your game, yes, it's allowed. But if you mean a non-vanilla client or mod, as long as it doesn't have an advantage over the other players, it's fine. You can find a list of allowed and not allowed clients/mods here. If it isn't mentioned, you'll be using it at your own risk. Remember if it provides a distinct, gameplay-changing advantage, it is illegal.