Alright, alright...I suppose I'm caught, so I might as well confess.
I know I'll lose my license. Heck, I could probably even go to jail. Man, I'd been trying so hard to be a doctor...I paid off so many people...
Anyway, Zeolito came to me after his fight. He was intending to sue my sister for assault. When I told him his leg wasn't broken, he asked me if there was any way we could fake a broken leg. He would pay me half of whatever he won. So I dusted off some old X-rays and had him admitted. I had no idea he was planing anything more than a little fraud.
That night, I happened to be at the hospital seeing another patient. I looked in on Zeolito at 12:30 and found his room empty. I didn't know what to do, so I pretended he was still there. Raising the alarm would have simply drawn attention to the fact that he could walk.
It seemed pretty simple. Zeolito was using me. Shortly after I gave the "do not disturb" order, he must have taken off his cast, climbed out the window, and found a way to get to Zeogoldilocks' office, maybe a taxi. He caught her there and tried to kill her. She must have turned the tables on him and killed him instead.
My sister has that Zeo family cleverness, so I'm guessing she saw the wristband on him and deduced that he sneaked out. After 1 A.M., when the streets were empty, she drove the corpse back in her own car. By wandering the halls, she figured out where room 507 was and planted the corpse beneath the window. If Zeolito had been found wearing street clothes, then people might conclude that he had left the hospital willingly. So, my sister stripped the body and then broke Lindo's leg for real.
It's funny, really. Zeolito worked so hard to give himself an alibi and all he wound up doing was giving his killer an alibi.

I knew my sister killed Zeolito, but I was trying to do whatever I could to keep my medical license. Seeing as I'm probably going to lose that anyways now, there's no point. At least this'll keep her from blackmailing me, which I'm sure she was planning to do.