The new signing has already impressed his team-mates, netting some brilliant goals in sessions this week.
And the Italian international was put through his paces again today as Slaven Bilic goes in search of three points against the Hornets.
The injury-plagued Hammers have so far struggled to hit the back of the net this season.
But they’ll be hoping Zaza can solve their attacking woes.
The side will also soon be boosted by the return of Dimitri Payet and Manuel Lanzini, who were spotted in training today.
Alvaro Arbeloa – who joined on transfer deadline day – was also snapped taking part in the session.
Click through the gallery above to see photos of Zaza in training.