The most reliable source for user-provided firmware is XDA Developers. Search for "AC8227l CVD1810-WJ update".
is the most comprehensive repository for "WJ" (ZXDZ-01) head unit firmware and recovery dumps. Video Tutorials XYAuto's YouTube channel cvd1810 wj update link
sha256sum cvd1810_wj_4.2.1-r17.fw
If you can tell me your and MCU version , I can help you find a more specific update link. The most reliable source for user-provided firmware is