How to upgrade Android - 5.0 Lollipop preview on Nexus5 and Nexus7 (2013)

Go to Android Developers
Download Android SDK Manager and Android - 5.0 Lollipop for Nexus5/Nexus7 images.
Install Java JRE 8
Install Android SDK

Use the commands under cmd to check your device is exist.
adb.exe devices (Power on)
or
fastboot.exe devices (Fastboot mode)
Unlock your device.
fastboot.exe oem unlock



Nexus5

Unzip hammerhead-lpx13d-preview-f7596f51.tgz to hammerhead-lpx13d-preview-f7596f51.tar
Upzip hammerhead-lpx13d-preview-f7596f51.tar
Open unzip folder and copy below files to path(Android SDK) X:\adt-bundle-windows-x86_64-20140702\sdk\platform-tools
bootloader-hammerhead-hhz12d.img
radio-hammerhead-m8974a-2.0.50.2.21.img
image-hammerhead-lpx13d.zip
flash-all.bat
flash-all.sh
flash-base.sh

And you have 2 ways to upgrade image.

Run "flash-all.bat" as administrator.
or
Run below commands:
fastboot.exe erase boot
fastboot.exe erase cache
fastboot.exe erase recovery
fastboot.exe erase system
fastboot.exe erase userdata
fastboot.exe flash bootloader bootloader-hammerhead-hhz12d.img
fastboot.exe reboot-bootloader
fastboot.exe flash radio radio-hammerhead-m8974a-2.0.50.2.21.img
fastboot.exe reboot-bootloader
fastboot.exe update image-hammerhead-kot49h.zip

Nexus7

Unzip razor-lpx13d-preview-ae4f461f.tgz to razor-lpx13d-preview-ae4f461f.tar
Upzip razor-lpx13d-preview-ae4f461f.tar
Open unzip folder and copy below files to path(Android SDK) X:\adt-bundle-windows-x86_64-20140702\sdk\platform-tools
bootloader-flo-flo-04.04.img
image-razor-lpx13d.zip
flash-all.bat
flash-all.sh
flash-base.sh

And you have 2 ways to upgrade image.

Run "flash-all.bat" as administrator.
or
Run below commands:
fastboot.exe erase boot
fastboot.exe erase cache
fastboot.exe erase recovery
fastboot.exe erase system
fastboot.exe erase userdata
fastboot.exe flash bootloader bootloader-flo-flo-04.04.img
fastboot.exe reboot-bootloader
fastboot.exe update image-razor-lpx13d.zip