ztodo list|ls [verbose]    -- Show all tasks
ztodo list|ls N [verbose]  -- Show task N
ztodo rm|remove N          -- Remove task N
ztodo done N               -- Done task N
ztodo undo N               -- Undo task N
ztodo doing N              -- Doing task N
ztodo clean                -- Rm done task
ztodo clear                -- Rm all task
ztodo add ...              -- Add task to list