The talks, which took place on Wednesday, also highlighted political impartiality from President Robert Mugabe's longtime loyalists in the police and military.
The 160-page draft, completed after three years of tension between hardliners and reformists during often bitter and violent nationwide canvassing, will be voted on in a national referendum slated for April, ahead of elections to end a shaky coalition formed after the last disputed, violent polls in 2008.
Regional mediators made a new constitution a key condition for fresh elections. Lawmakers will not be able to change the draft unless there is a last minute revolt against it in the legislature, Veritas, an independent legal monitoring group, said on Wednesday.
There was no immediate sign of that in the Harare Parliament House on Wednesday.
Paul Mangwana, co-chair from President Mugabe's party of a parliamentary panel in charge of rewriting the Constitution, told legislators the lengthy, delayed process cost about $45-million.
"It has been a long journey and we think [we] did our best for the country," Mangwana said.
He described the funding, including United Nations and foreign donations, as money well spent.
"People will ask why, but democracy is very expensive," Mangwana said.
All main party leaders have called for a "yes" vote in the referendum after years of violence, uncertainty and economic meltdown that has left the nation weary and demoralised.
The Parliament debate is expected to wind up after several sittings in coming days, followed by a month for distribution of the proposed constitution to electors nationwide, said Veritas.
The draft shows Mugabe's Zanu-PF party and Prime Minister Morgan Tsvangirai's Movement for Democratic Change both made concessions over points in dispute.
According to the proposed constitution, a person can be president for a maximum of two five year terms, but the term limit is not retrospective.
That means Mugabe, who turns 89 this month and has been in power for 33 years, can run for president again and if he wins could rule to the age of 94, and even to 99 if he ran for, and won, a second term.
But according to the draft, Mugabe would no longer have the power to veto legislation and presidential decrees, which Mugabe has often used unchallenged, would need parliamentary approval, mostly by a two-thirds majority of lawmakers.
The president would not be able to arbitrarily appoint the 10 powerful provincial governors from his party and provinces will be able choose their own chair, or premier.
Peace and reconciliation commission
Increasingly frail at public appearances, Mugabe is seen to have recently lost much of his trademark combative spirit. Tsvangirai's party agreed not to insist that presidential candidates nominate a running mate for the next poll, so Mugabe will not have to pick a possible successor in his fractious, rivalry-ridden former ruling party. The draft allows the victorious president to personally appoint two vice presidents.
The new constitution binds the police and military to be impartial and not to "further the interests of any political party or cause". Military commanders, accused of condoning past political violence blamed on Mugabe militants, have refused to salute Tsvangirai (60), repeatedly vowing allegiance only to Mugabe – the nation's first black ruler and leader of the guerrilla war that led to independence from Britain in 1980.
A beefed-up Constitutional Court with powers over all other courts and the new peace and reconciliation commission are proposed as reforms to a judicial system critics say has long been packed with pro-Mugabe judges and officials.
The Constitutional Court would deal with violations of the charter and abuse of power or governance.
The proposed constitution says the often violent seizures of white-owned farms since 2 000 restored land to black people who were "unjustifiably dispossessed" of it by colonial-era settlers and states that the seizures cannot be reversed.
The new reconciliation body was praised as "a hopeful sign that victims of political violence may obtain some justice" by the Open Society Initiative for Southern Africa, a non-governmental organisation that encourages democracy.
Despite continuing arrests of rights and democracy activists in Zimbabwe, the Constitutional changes represented some "significant gains", said the organisation.
The Open Society Initiative for Southern Africa said the proposals were "better than feared but far from ideal". – Sapa-AP