Perhaps in this case it’s going to be easier to paste this command:
set PATH="%PATH%;C:\Program Files (x86)\Minimal ADB and Fastboot"
as the first line into
flash.bat. The original contents of the
flash.bat should then start on the second line (i.e. we’re adding a single line at the top). After this running flash.bat should give the desired result.
What the command does, is tell flash.bat where it can find the fastboot program on your system. Fastboot is able to find your phone (judging by your previous screenshot), so that’s all good to go. What you’re getting stuck at, is the cmd only knowing about the fastboot command when you’re in the exact folder it is installed in. As said, the command just adds the folder where you’ve installed fastboot to the places to look for commands that aren’t in the folder in which you’re working.