The way I do this one is to do a big running jump from the top level of the big rock with the journey to the next biggest rock that is right next to it.
From the next biggest rock, I do a running jump directly to the platform with the door.
To do the running jump, press and hold the forward arrow + a shift key, and a half-second later press and hold the space bar, too.
If I press all the keys at the same time, I merely jump in place, so the spacebar has to be delayed just slightly.
I do this jump in third person. It's easier to line up the avatar with the destination, and to see where your feet are landing.
Hope this helps someone.