Default How to unbrick asus memopad 8 ?

Hello
I am newbie

I have asus memopad 8, someone installed Chairfire 3d on my tablet, so It can't boot anymore, I only saw the loading asus logo.
My tablet is rooted, I tried to install stock rom by using default recovery (Power + Vol up) but: installation aborted.
i.imgur.com/2LNWyQc.jpg
I installed Rockusb devices driver do use rkandroidtool, but rkandroitool didn't detected my device.
i.imgur.com/ShI2BPb.png
I am using Win7 ultimate 32bit

So please help me, I have tried many ways for 3 days but not succeeded
PS: I don't know why the device automatically disconnect from my PC, then I must re-connect the usb cable