Plug-in Hybrid Electric Vehicle. It's the most complex drivetrain you can possibly buy with a full gas engine and transmission mated to a full EV with external charging support.
I can't speak for other PHEV drivetrains but the Toyota PHEV design isn't that complex. It uses an ingenious planetary CVT with a small gas engine instead of a full gas engine and regular transmission.
Also, because the gas engine mostly runs at its most efficient RPM, there is little stress on it so it runs very reliably.
