I used to worry about power management... until I realized that the computer did a pretty good job of managing power all on its own (the CPU only consumes ~1.9 W / core at full tilt with SMT enabled (12 cores)... ~3.8 W / core with SMT disabled (6 cores))... what I really wanted was a way to turn the screen off when I was done for the day.
But if you look in:
Zorin menu > Settings > Privacy > Screen Lock
-- and --
Zorin menu > Settings > Power
... you should find what you need.