Discussions between the London clubs are progressing over a deal worth in the region of £25million, which would pave the way for Chelsea to move for Sevilla’s Jules Kounde.
Zouma, who has not featured in either of Chelsea’s first two games of the season, is understood to want an increase in wages to over £100,000-a-week, although there is optimism that personal terms can be agreed.
West Ham manager David Moyes is desperate to bolster his squad with new signings before the end of the month and has made a centre-half a priority, with the club having also targeted Fiorentina’s Nikola Milenkovic and Marseille’s Duje Caleta-Car.
Zouma, who did start the Uefa Super Cup win over Villarreal in Belfast earlier this month, joined Chelsea from Saint Etienne in 2014, and has spent seasons on loan at Stoke City and Everton.
The France international played regularly under Thomas Tuchel last season, scoring five goals, but has found opportunities at Stamford Bridge further squeezed by the emergence of academy graduate Trevoh Chalobah.
Chelsea had hoped to use Zouma in a part-exchange deal for Kounde but he wanted to stay in England and London.
If he joins West Ham, Chelsea are set to make a straight bid for Kounde, whose release clause at Sevilla is set at £68m.
“I think it’s a great time to be West Ham,” said the defender. “I’ve been here for many years and I’ve seen a lot of things changing and my relationship here with everyone is like a family. When you’re in a family, you have good moments and bad moments, but you have to stick with it and you don’t give up.
“In every process, there are negatives and positives and that’s the way to get though things and this is the result of our process. I think all our fans are so proud of us.”