Flash it using system update. To do this follow the step :
1. Download the file that attached in this post. For unroot download RootDisabled, for rooting your device download RootEnabled file.
2. Change the name to update.zip and place the file that you downloaded into internal memory of your device
3. Open Setting->System Update
4. Touch threedot menu on the upper right, and touch Reboot in mode Recovery.
5. Apply.
Updated: If you have problem to update MIUI 6 v6.7.1.0 to MIUI 7 v7.0.5.0 apply the Restore_defaults_6.7.1.0.zip, only change it to update.zip in your root folder and use the your recovery.
more info MIUI forum
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