Obtaining ZTE router firmware is not a straightforward process like downloading drivers for a graphics card. ZTE operates on a Business-to-Business (B2B) model, supplying hardware to Internet Service Providers (ISPs) rather than selling directly to consumers in many markets.
Consequently, there is no single public repository for ZTE firmware. Firmware is highly specific to the hardware revision, region, and ISP customization. Installing the wrong firmware will permanently "brick" the device. zte router firmware upgrade download link
A ZTE F670L router is not a singular entity. Manufacturing revisions often change internal chipsets (switching from Broadcom to Qualcomm or Realtek chipsets). A firmware binary designed for Hardware Version 1.0 will likely fail to boot on Hardware Version 2.0 due to driver incompatibility. Obtaining ZTE router firmware is not a straightforward
If ZTE and your ISP have no public download link, you have three options: A ZTE F670L router is not a singular entity
Once you have the legitimate link and the downloaded file, follow this process.