Yes, definitely. Valuev was hurt badly by 210 lbs David Haye and was stunned by light-hitting skinny southpaw Jean Francois Bergeron. He won't took a lot of punches from 280 lbs guy with enormous power and good precision.
If Valuev can lean all over Zhang though and start throwing that dumb right hand Zhang may collapse from exhaustion.
Prime Haye is probably top 10 hardest hitters of all time. (Years 2007-2009) So I wouldn't look too much into that shot where he rocked Valuev in the last round, when Valuev was already tired.
How Haye wasn't prime when he fought Wlad and Chisora? He was young and against Chisora he looked better than ever. Against Wlad he didn't have much success at the offensive end, but his speed and reflexes looked incredibly good. And yes, Haye was great puncher, but Zhang is 70 lbs heavier great puncher. I have no doubt he hits harder than Haye
In 2008 I remember reading magazine where they had measured Haye's punching power and it was harder than any heavyweight of that era. In Wlad fight Haye had injured his toe, so he wasn't 100%. Basically bad injuries ruined many of his big fights. And I agree that Zhang hits harder, but power is not everything. Especially against 330lbs Valuev who had granite chin.