One wonders if engineers dreamed this creation on a chalk board or bar napkin. BMW offered the Z3 with 11 different engines ranging from a 1.8 L M43B18 inline-four making 118 hp to the 3.2 L S54B32 inline-six making 315 hp. However BMW built this prototype in 1999 to prove any of their engines could fit into a Z3. This Z3 prototype now has a naturally aspirated 5.4 L M73 V12 from a E38 7-Series in the engine bay.
Source: BMW M FB page and Car & Driver