1. First, make sure that the downloaded zip brush package is complete and not damaged. Download the zip brush package again, and make sure that the downloaded file is the same size as the source file.

2. Second, check whether the device is already root. If the device doesn't have root privileges, it can't install unsigned zip brush package.

3. Finally, use the brush tool or method to install the zip brush package. The option of signature verification will be provided, and these tools will be used to install the zip brush package.