In some of the supplementary documentation for this press release, you can see the government's case for seizing Zhang's assets on the grounds that they are traceable to a different convicted criminal (Ulbricht, who is the victim of Zhang's fraud), whose assets were already forfeited due to Ulbricht's conviction.

I'm curious though, if Zhang had not plead guilty and the government had not succeeded in getting a wire fraud conviction for Zhang, would their argument that the assets are forfeitable under Ulbricht's conviction have failed also? In other words, was it necessary to convict Zhang to finish seizing Ulbricht's assets, or could they have won a case for seizure without a conviction for Zhang?