Two boots are on two skis moving very fast.
A person is skiing very quickly.
A pair of skiing boots and skis might not be on a person. It could be a pair of empty ski boots clipped to their skis going down a hill, or possibly a skiing robot. It is also possible the boots are not skiing at all- they could be moving very fast because they are being carried on a sled or other vehicle.
exists e1 p1 s1 x1.(for(p1,e1) & r_very(e1) & a_fast(s1) & Manner(e1,s1) & Actor(e1,x1) & v_move(e1) & exists x2.(on(x1,x2) & n_ski(x2) & card_eq_2(x2)) & n_boot(x1) & card_eq_2(x1))
exists e1 s1 x1.(r_very(e1) & a_quickly(s1) & Manner(e1,s1) & Actor(e1,x1) & v_ski(e1) & n_person(x1))