While Bottas continuing with the Swiss outfit was a formality, there had been some question marks over Zhou.
However, the Chinese driver has now been signed for a third year with the team, which is expected to revert to the Sauber identity for the next two years, ahead of the full transition to the Audi name in 2026.
Current Formula 2 championship leader Theo Pourchaire will also remain in his reserve and simulator driving role.
"The decision to continue our journey with our driver line-up unchanged is testament to the investment we have made in our project," said team representative Alessandro Alunni Bravi.
"Nothing in F1 changes overnight, and we have taken a conscious decision to focus on stability and to keep building our team up together as we embark on an important period of transition.
"Valtteri and Zhou are drivers of known talent and skill, and they work really well together. They are well-matched and can push each other.
"Valtteri has taken a real leader's role within the team, pushing us all to give our best. Zhou has made impressive steps forward in the last two years and we expect him to continue on this trajectory in 2024.
"Now the baton is back to us – we have to give both drivers a good car and put them in the best conditions to perform."
Zhou's confirmation means that he will finally get a chance to race in his home country next year after COVID led to the Shanghai event's absence from the calendar from 2020 to 2023.
"Signing again with the team is always a great feeling, especially when we know how things are shaping up," he said. "I am proud to be part of Alfa Romeo and grateful for their trust.
"I have been working extremely hard since day one and there is an incredible level of motivation to keep doing so every day forward.
"My relationship with Valtteri is really good, and we are working closely together and with the team to push everyone forward.
"I am also very excited about the opportunity to finally race with my team in China, in front of my home crowd. It will be a great moment and I'm proud to be able to share it with all those who have supported me."
Bottas insisted that good progress is being made by the team, even if it has struggled for performance on track this year.
"I have a feeling we have an exciting journey ahead of us, so I am happy and grateful to be able to look forward to 2024 knowing how the team is shaping up," said the Finn.
"There is a good atmosphere within our squad, I get along with Zhou and we both push each other hard to improve.
"There is an impressive amount of work going on behind the scenes, in Hinwil and beyond, and now that the line-up is set for next year, we can focus fully on improving, starting this weekend in Singapore already.
"Every step forward we make is a step forward for this year and next, so we are motivated to give everything we have every time we're trackside or at the factory."
