Harry was spinning, around and around, getting dizzy and dizzier, and the ground coming up to greet him. The ground seemed to be enthusiastic about greeting him. Harry pulled out his wand as he was falling and tried to summon the broom to him to break his fall, but his spell was lost in the wind and Harry, with out thinking a second about it, reanimated the ability to access nonverbal spells through the traumatic experience of facing death, not only unexpectedly, but without anything to do about it. But he instinctively summoned the broom still floating a hundred feet above.
Now it was a race, Harry could see the spell had worked, but he had picked up speed and was still gaining. The broomstick was coming faster but was it fast enough. The ground was coming up real close now.
The broom came up under him and Harry dived, knowing that pulling out of the dive at to great a speed could result the same way as hitting the ground. At the last minute, Harry pulled up and narrowly avoiding the rough equivalent of creamed spinach.
It was then that Harry realized that, during the near fatal plummet, the invisibility cloak had come off. Harry looked around avidly; he saw it, still fluttering down from the tower. As Harry was so low, it was slowly making its way to him, so he picked up speed and caught it. He floated there for a minute while he adjusted the cloak so that it covered him and the broom, before flying back up to the balcony. The Death Eaters were crowded around the balcony edge; all of them were still bearing looks of utmost surprise from when they saw Harry appear from no-where fifty feet below. But now most of them were shaking their heads and backing up from the balcony.
Harry mutely stunned another Death Eater that had lingered by the balcony edge when he flew past. Luckily the other Death Eaters were still significantly shocked that they hesitated before sending three spells towards some point ten feet below Harry. Harry slowly ascended and was well over their heads when he released his impediment jinx. This time, the Death Eaters retaliated before Harry's spell had even gotten halfway to the tower. Greyback fell over as a result of Harry's jinx. Two down, Harry thought, five to go.
But even as he thought this, Harry saw Dumbledore, using the Death Eaters' distracted attention as another advantage. Dumbledore was quickly and silently striding over towards where Snape lay unconscious. A memory stirred in Harry's mind as usual it was Mr. Weasley's voice being all advisable, "Smart thing to do, not using their own wand, which could have betrayed them." And Harry realized with a jolt that Dumbledore could not risk using Snape's wand to incapacitate the Death Eaters.
Looking back to the landing, Harry saw Dumbledore mutely wave his wand. When none of the Death Eaters fell down, Harry reminded himself that Dumbledore being the greatest wizard of the day, would not be as stupid as to use another wizard's wand to cast a major spell.
Whatever happened next happened faster then Harry could correctly follow, though Dumbledore told him what happened shortly after.
Dumbledore non-verbally summoned his wand from the ground below so that he could cast more powerful spells. When the wand flew up over the balcony, the Death Eaters watched it fly by and into Dumbledore's hand. Before any of them could react, Dumbledore had conjured invisible ropes and tied up the half dozen Death Eaters.
And for a rather lame ending, Snape, and the others were sent to Azkaban and stayed there to rot, until Vold—sorry He-Who-Must-Not-Be-Named released them and punished them for failing. "Thankfully", Malfoy's mother and Malfoy himself, were saved from being murdered for failing.