The sad part was that what he was accusing her of was exactly what he didn't want to be. Zacharias Smith didn't want Cho in his life because he was the only one left. He didn't even want her because she thought she owed Cedric something. If she was going to be in his life, she needed to actually be there. And without knowing the why he would keep pushing, testing to see how far this could go.
"And then what?" While Zacharias didn't think he was going to live forever, he didn't think he would ever rank in the same league as Cedric or Potter. So, he hardly felt like he could be her third strike - whatever that meant. "Cho Chang alone forever? Or worse stuck lying about the fact she's baby sitting my miserable existence out of some shit obligation?"