Sony Tablet Z4 Factory Reset

If you forgot pin or password, how to reset Sony Tablet Z4 to default ?

Almost google’s results are wrong because great or cleverly SEO technology.
Don’t waste time on google it.

Even Sony web FAQ cannot give this information

the answer is in Sony Z4 manual,

If you forget your screen unlock password, PIN or pattern, you can use the device repair
feature in Xperia™ Companion to erase the security layer. You need to provide your Google
account login details to perform this operation. By running the repair feature, you reinstall
software for your device and you may lose some personal data in the process.

1. download Xperia Companion
2. un-plug USB cable from Z4 to PC, and choice repair software
3. Following the step and it will finish reset whole system to factory default soon

But I don’t know how to reset to default without software.