Can you access fastboot, vol down and power button to power on phone.
Can you access recovery, vol up and power button to power on phone
If you can access recovery install the latest update.zip
If you cannot access recovery and can access fastboot, read here https://forum.meizufans.eu/topic/6550/guide-recover-a-meizu-m3-from-bootloop-meizu-logo-and-constant-reboot
If you cannot access both your phone is likely died.