The ZTE Optus X Vista (model Z6621O) is a budget-friendly 4G smartphone available from the Optus carrier in Australia. It runs on the lightweight Android 11 (Go edition) to ensure smooth performance on its entry-level hardware. Powered by a UNISOC (Spreadtrum) chipset, this device is ideal for essential communication and daily tasks. This guide provides the official Optus Australia stock ROM (.pac file), which is essential for unbricking the device, fixing software bugs, or removing a Google FRP lock.
Important: This firmware is specifically for the ZTE Optus X Vista (Z6621O). The flashing process for UNISOC/Spreadtrum devices is very specific. Flashing the wrong firmware on a different model will cause a hard brick.
Quick Device Specs
- Device: ZTE Optus X Vista (Z6621O)
- Release year: 2021
- Chipset: UNISOC SC9863A
- Display: 6.5″ IPS LCD, HD+
- Battery: 4000 mAh
- Original OS: Android 11 (Go edition)
Required Downloads
To flash a Spreadtrum/UNISOC device, you will need the specific drivers and flashing tool. You can find the downloads for these in our main guide linked below.
- SPD Upgrade Tool or SPD Research Tool
- Spreadtrum/UNISOC USB Drivers
Stock ROM (Firmware)
| Region / Carrier | Build | Android | Type | Download | Chipset |
|---|---|---|---|---|---|
| Australia (Optus) | V1.0.0B19 | 11 (Go) | SPD .pac Firmware |
Download | UNISOC/SPD |
How to Flash the Stock Firmware
Flashing the stock ROM onto your ZTE Optus X Vista requires a Windows PC and the SPD Upgrade Tool. The process involves installing the correct UNISOC drivers, loading the .pac firmware file from the download into the tool, and then connecting your powered-off phone while holding the Volume Down key to initiate the flash. This will completely restore your device to its original Optus software and will erase all data.
For detailed, step-by-step instructions with screenshots, driver and tool download links, please follow our comprehensive pillar guide: How to Use the SPD Upgrade Tool to Flash Your Smartphone.
Device-Specific Troubleshooting for Optus X Vista
- Correct Driver Installation: The most common failure point is incorrect drivers. If the tool doesn’t see your phone, you must install the Spreadtrum/UNISOC drivers, which often requires you to disable ‘Driver Signature Enforcement’ in Windows first.
- Using the “Boot Key”: To initiate the flash, power the phone off completely. Press and hold the Volume Down button, and *while holding it*, connect the phone to your PC with the USB cable. The tool should then detect it and begin the process.
- Fixing Google FRP Lock: If you are locked out of your phone by Google’s Factory Reset Protection (FRP) after a factory reset, flashing this stock ROM will perform a complete wipe and remove the locked account, allowing you to set it up again.
- Carrier-Specific Firmware: This is an official ROM for the Optus Australia network. It will restore all Optus branding and pre-installed applications. It will not remove the SIM lock from your device.
FAQs
Q1. What is Android 11 (Go edition)?
Android Go is a lightweight version of the Android operating system, specifically designed by Google to run smoothly on entry-level smartphones with 2GB of RAM or less. It includes optimized “Go” versions of popular Google apps.
Q2. Can I use this ROM on a non-Optus phone?
It is strongly advised against it. This firmware is carrier-specific. Flashing it on a device from another region or a different carrier could cause issues with cellular network connectivity (no signal) or brick the device.
Q3. Will this process erase my data?
Yes. Flashing the stock ROM with the SPD Upgrade Tool will perform a full factory reset and completely wipe all personal data, apps, and settings from your device.
Q4. What is a .pac file?
A .pac file is a packed firmware file used for Spreadtrum/UNISOC chipsets. It contains all the necessary partitions—system, boot, recovery, modem, etc.—in a single, integrated file for flashing.
