How can I root my H7 (Marshmallow, build B320)

[Xenosender]

Hi all

I successfully updated my H7 to Marshmallow & build B320 (EMUI 4.0)
I could after that install the chinese version of TRWP (2.8 I think, available on most tutos on how to install custom recovery and root)

However, impossible to root my device, despite using several Update-superSU versions which either :
- put the phone in bootloop
- put the phone on blackscreen after the boot logo
- went to completion, phone started but superSU app says "no root installed"

has anyone succeeded in rooting on the same config ?
Through which method ?

Thanks for any help!