Bottas had hoped to remain with the organisation for a fourth campaign, having joined from Mercedes at the end of the 2021 season.
Zhou will also not continue with the team, leaving Sauber with an all-new pairing for 2025.
It’s expected Sauber will announce Gabriel Bortoleto as team-mate to the already-confirmed Nico Hulkenberg.
“A situation like this is never easy for anyone,” admitted Bottas.
“But after all the good and in-depth discussions we had in the past weeks, we realised that the conditions to grow this project together were not met.
“These past years with the team have been an incredible journey, full of growth, challenges, and unforgettable moments.
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“I’m grateful for the joint experiences as well as the trust and support I’ve felt every step of the way.
“Though it’s time to move on, I’ll always carry a piece of this team with me, and I look forward to seeing what the future holds for us both.”
Sauber boss Mattia Binotto added: “We extend our deepest gratitude to Valtteri for the past three years together.
“He has been the embodiment of professionalism, using his vast experience to support the team’s growth.
“Valtteri’s dedication and approach have been invaluable during a pivotal time in our history, and the memories of these years will stay with us for a long time.
“In considering our driver line-up for the coming seasons,
“Valtteri was unquestionably a key candidate.
“With his fighting spirit, he frequently pushed the car beyond its performance limits.
“However, a decision had to be made. After open and constructive discussions, we mutually concluded that final conditions could not be met so we agreed that it is time to part ways.
“Valtteri will always have an open door here in Hinwil.”
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