When a load's lifting points are not on the same plane or elevation, the tension in each sling must be calculated in a little more formal method.
Use the panels from the Journeyman and Master Rigger Reference Cards pictured below to (1) determine the tension for each sling leg and (2) the proper shackles and slings for the job. Answers can be found below.
Journeyman Rigger's Reference Card - Panels 3 & 5
Master Rigger's Reference Card - Panel 10