This fits with the Sky Sport Italia report that Zaza will be on loan with commitment to purchase for a sum of €28m, including rewards.
The choice to purchase will get to be obligatory after a modest bunch of appearances in the Hammers shirt.
The striker flew out to London on Friday for conclusive transactions after Juve acknowledged the proposition.
It's the main raid abroad for the 25-year-old, who spent his profession at Atalanta, Sampdoria, Juve Stabia, Viareggio, Ascoli, Sassuolo and joined Juventus in 2015.
The Bianconeri sold him to Sassuolo for €10m in 2013 with a purchase back choice for €18m enacted two years after the fact, so to all goals and purposes he cost the club just €8m.
This speaks to a colossal €20m benefit from offering the Italian, who has one objective in 14 senior tops.
Last season Zaza scored eight objectives and gave two helps with 24 aggressive appearances for Juve, a hefty portion of them off the seat.
He most broadly found the net in stoppages for a definitive Scudetto standoff win against Napoli in February.
West Ham United had been in contention for the Europa League, however were thumped out in the play-off by Astra Giurgiu.