the Rhodesia settlement talks moved into their second phase today and immediately ran into disagreements as the Zimbabwe-Rhodesian government flatly rejected Britain's suggestion that Prime Minister Abel Muzorewa step down during a transition period.

Britain had suggested such a move to Muzorewa earlier this week as part of a plan in which the Salisbury Parliament would be dissolved and London would temporarily resume authority in its rebel colony, using a British administrator, military and police, until elections could be held under a new constitution.

The Zimbabwe-Rhodesian government said it "rejected out of hand" this proposal, however, and its foreign minister, David Mukome, said today that his government and Parliament would continue to control the day-to-day operations of government pending election results.

The differences that emerged today among Britain, the Zimbabwe-Rhodesian government and the rival Partiotic Front guerrillas were not surprising. It is generally acknowledged that the talks on the transition, involving elections, disposition of the warring military forces and a cease-fire, will be far more difficult than the just-concluded, 38-day talks that produced agreement on a constitution for an independent Zimbabwe.

The nature and depth of the differences, however, demonstrated the difficulties Britain still faces in trying to bring about a negotiated settlement of the intractable 14-Year-old independence issue.

Taking a tough stance, Mukome said the present talks were merely over implementation of the new constitution, which removes significant areas of control by the white minority.

Mukome noted that Britain had never exercised direct governmental authority in Rhodesia and he did not expect any agreement at the London conference to ignore this history.

Muzorewa also said transitional proposals presented by the Patriotic Front last month were "totally unacceptable." These call for an eight-member governing council during the transition, equally divided between the Front, on one side and the British - and the Muzorewa administration on the other. Britain has also turned down the Front proposals.

Patriotic Front spokesman Eddison Zyobgo said "it is preposterous to suggest" Muzorewa would stay in power during the transition. "It is the intention of the Patriotic Front -- and apparently shared by the British -- that there will be some other administration during that period. It is no time for delusions."

The Front also sharply differed with preliminary suggestions by british Foreign Secretary Lord Carrington that the interim period should be as short as possible with elections to be held two months after agreement at the London talks.

The British apparently want to get in and out as quickly as possible to avoid becoming involved in a long-term commitment like Ulster that could be politically difficult.

Carrington cited fears that the proposed cease-fire could break down if there were a long transition period. Thus, he said, there would not be time to register voters or to set out voting constituencies.

Instead, he said, observers could be used to prevent fraudulent voting and rather than having individual constituencies there could be nationwide proportional voting for parties with each party having a list of candidates in order of priority. This system was used in the controversial April elections that brought Muzorewa's internatinally unrecognized black-led government to power.

Zvobgo said the Front wanted a six-month transition, registration of voters and constituency voting. Aside from these issues, he said, it would be impossible in two months to bring about a cease-fire in the seven-year-old war, release thousands of persons from detention and martial law in 90 percent of the country and hold election compaigns.

He noted that at the abortive Genva conference three years ago Britain wanted a 15-month transition and then-rhodesian Prime Minister Ian Smith held out for 21 months.

There was no discussion today of the most contentious issue in the transition, what to do with the warring military forces, a key point for the white minority of 230,000. Britain has hinted that some senior British military officers might be brought to run the white-officered but mainly black Zimbabwe-Rhodesian forces, something that would be unacceptable to the guerrillas.

Control of the military is seen as having a major potential influence on the outcome of the election.

The factions agreed that Carrington should present a document at the next meeting, expected to be Monday, outlining his ideas for the transition.