Section Hall.
Implicit Type gT : finGroupType.

Theorem SchurZassenhaus_trans_sol gT (H K K1 : {group gT}) :
solvable H -> K \subset 'N(H) -> K1 \subset H * K ->
coprime #|H| #|K| -> #|K1| = #|K| ->
exists2 x, x \in H & K1 :=: K :^ x.