OK, I see where you mean now - RH after marcatissimo.
Don't stetch the whole tenth, use 1-2 or 1-3 (1-2 if the top note of those two is black, 1-3 if the bottom note is) on the bottom notes and move your hand to reach the top one (with 5), keeping 2/3 over (just touching or just above) the top of the bottom two.
Start slowly, and, if it helps, do the initial run throughs actually holding that 2/3 note down throughout until your comfortable. Then play it as written, slowly, and then speed it up.