What is the test for concurrent sentences for two convictions of conspiracy to murder under section 654 of the California Criminal Code?

"The purpose of section 654 is to prevent multiple punishment for a single act or omission, even though that act or omission violates more than one statute and thus constitutes more than one crime. Although the distinct crimes may be charged in separate counts and may result in multiple verdicts of guilt, the trial court may impose sentence for only one offense...." (People v. Liu (1996) 46 Cal.App.4th 1119, 1135, 54 Cal.Rptr.2d 578 [concurrent sentences for two convictions of conspiracy to murder were proper because each conspiracy involved a separate victim; however, separate punishment for offense of carrying a silencer could not stand where the objective of the crime was the successful completion of the conspiracies].)