LG Optimus Zip L75c hard reset
In the case of a malfunction or lock up error, press and hold the Power/Lock Key for 8 seconds to reset.
(Caution: If you perform a factory reset, all user applications and user data will be deleted. Please remember to back up any important data before performing a factory reset.)
You can use LG Mobile Support tool to repair your LG cell phone, after download select menu Customer Support > Recovery Phone
Go to Support > Mobile Phone Support > Select the Model (L75C)