Provide the following and I will give explicit steps:

and a specific update tool (often labeled as "F97" or similar in community guides). ZTE Official Website Standard Update Process (Web Interface)

ZTE’s default dashboard is surprisingly clean. It doesn’t try to be a spaceship. You get a clear look at your data usage, signal strength, and connected clients. For the average user, having a UI that loads instantly on a mobile browser without needing a degree in network engineering is a massive win.

Official firmware and user guides are distributed regionally. You can often find the latest version for your specific region on the ZTE Device Support page Regional Availability

ZTE does host a public firmware archive. However, legitimate sources include: