The motion is now due to be presented to parliament later today.
Senior party member Paul Mangwana said the process could take as little as two days to complete, and President Mugabe could be removed by Wednesday.
A deadline set by Zanu-PF for his resignation passed on Monday.
Separately, military leaders said they had planned a “roadmap” for Mr Mugabe’s future, and that the ousted former vice-president, Emmerson Mnangagwa, would return to the country soon.
Grace Mugabe and Mr Mnangagwa had both been seen as potential successors to the ageing president.
But earlier this month, Mr Mugabe fired his deputy – widely seen as an endorsement of his wife – prompting a military intervention.
The country’s top general says Mr Mugabe and his former deputy have been in contact, and would hold in-person talks soon.