By "Xeni Cutback", do you mean the section between Xeni Pass and The Elephant? That's on the route anyway. From Mlambonja, drop down into the Kwakwatsi and pick up a trail heading upriver (on the western banks). This trail tends to want to take you straight to the Elephant via the second last side valley coming in from the side (and thus bypassing Xeni Pass). I would walk right to the end, ie walk out the main valley. At the bend, you'll notice some gullies going down (which look like passes) - at this point you could make a quick excursion loop to the summit or end of Mlambonja Buttress and back (yes, its worth the look). If you have lots of time then simply stick to the edge all the way from Mlambonja. Continue along the river as it bends, pass Xeni Pass and continue on to the Elephant - the exact route is up to you - hug the edge or plod straight up grassy slopes...odd cairns exist along either way (note a large free standing tower along the way - you can only see that its free-standing from close). Directly behind the Elephant, at a neck, you can decide to descend Elephant Gully directly infront of you (taking you directly to Cockade Pass via a trail), or ramp up the grassy summit above the neck and pick up a trail taking you to Cockade more or less via the escarpment edge.
I think Cockade is a pretty fast direct route back down, so do Tseke if you want to do it specifically, I don't think its faster.