The single line diagram in this brochure
gives a good idea of the configuration: one 12-cylinder ("father") and one 9-cylinder ("son") engine in each engine room. However, nothing short of the actual general or machinery arrangement drawings will give you a definite answer; the Significant Ships drawings about Viking Star excluded engineering spaces. However, considering the fact that the engine casing is aligned exactly with the main fire bulkhead, I'd say the engine rooms are located end-to-end: aft engine room in main vertical zone no. 1 and the forward engine room in main vertical zone no. 2.