Hi soleilsword,
Reducing the power consumptions really depends on what your project is trying to achieve.
It's probably worth reading Chapter 16 - Power Manager (PM) section of the SAMD21 datasheet.
The PM is able to disable selected on-chip peripherals, such as ADC, DAC, timers, RTC and sercom modules. The Arduino Zero core code activates most of these peripherals.
The SAMD21 also has 3 idle modes, at various states of idleness that affect whether the high speed (AHB) and peripheral (APB) buses are active, as well as the lowest power standby mode.
It also supports sleepwalking peripherals that allows them to to be woken up, while the CPU remains in soundly asleep in standby mode.