Click on or manually drag and drop the folder structure ( data/sprite/... ) of your 0-delay files into the open archive.
Many official and private servers have tried to counteract this. They implement a Min_skill_delay_limit (often set to 30ms or higher) or attempt to parse the .ACT file on the server side to validate the animation length. However, removing the frames in the client effectively breaks this server-side check, as the client reports the action as complete instantly. Ragnarok 0 Delay Sprite Grf