In the space of 48 hours this month, Prime Minister Robert Mugabe demonstrated his mastery of the political scene in Zimbabwe.

First he fired his former coalition partner Joshua Nkomo Feb. 17 after a carefully orchestrated anti-Nkomo campaign. Many analysts had feared that any such move could unleash civil strife, but so far, more than a week and a half after the humiliation of the leader of the Ndebele minority tribe, there have been no reports of unrest.

Then, two days after eliminating his biggest political threat in the black community, Mugabe turned his attention to his opponents of old, the now-depressed, diminishing white community.

In an unprecedented meeting in Parliament with about 70 white business and professional leaders, Mugabe offered an olive branch, saying, "Many of the white community are fuming within themselves, allowing a despairing state of mind to develop. Let us from now on be a little more accessible. Let us talk to each other."

To those listening carefully to Mugabe during the past two years, nothing he said was new. What was news was the event itself, since most of the prime minister's remarks about whites during the past few months centered on alleged sabotage and subversion, helping create an acrimonious atmosphere.

Like any good politician, Mugabe has now signaled that he is changing the pace and lowering the political temperature, at least temporarily.

Mugabe's timing coincided with two important visits. The British foreign secretary, Lord Carrington, who molded the peace settlement that resulted in Rhodesia becoming Zimbabwe and Mugabe coming to power, came Thursday for a visit. This week David Rockefeller, the former chairman of Chase Manhattan Bank whose name is synonymous with capitalism, is to visit this young nation that is struggling to introduce socialism to an economy dominated by private enterprise.

The violence, however, that was feared in many quarters with the removal of Nkomo still could come.

"It would only take a spark, like a beer-hall brawl, to start things," a Western diplomat said. Every day, however, it becomes less likely.

Nkomo has been careful to caution against such violence.

A high-ranking officer in the military said that since Nkomo's dismissal no change has been evident in the Army, where former guerrillas loyal to Mugabe and Nkomo are integrated with the former Rhodesian forces they fought in a seven-year independence war.

"Everyone has carried on as normal," he said. "They've either ignored or accepted the change."

Josiah Chinamano, who was fired as transport minister but is the vice president of Nkomo's Patriotic Front party, said he still supported the prime minister and would work for the merger of the Patriotic Front with Mugabe's Zimbabwe African National Union party.

Last week the Patriotic Front Central Committee decided to allow its one remaining minister and two deputy ministers to stay in the Cabinet, a backdown for Nkomo, who originally said all his party's ministers would leave the government and go into opposition after the prime minister fired four of them. This allows Mugabe to maintain the fig leaf of a coalition.

The long-term result of last week's dismissals is likely to be a hastening of the movement toward the one-party state that Mugabe advocates. Nkomo's weakened party is likely to see unity with Mugabe's party as its only avenue to a share of power since its minority tribal base would seem a barrier to it ever gaining power alone.

A failure to heal the rift, however, could have serious long-term repercussions for Zimbabwe. If the Ndebele minority were to became permanently disaffected and to feel no involvement in government, it could become a base for dissidence--one that could be used by neighboring South Africa.

The whites are already in the position of feeling they have no role in the government. Mugabe tried to assuage those feelings, saying he hoped to appoint more white ministers and adding, "We will not pursue a policy which deliberately sends whites out of the country. We are committed to a nonracial society."

The offer of ministerial posts was conditional, however. They would not be offered to members of the Republican Front headed by Ian Smith, the former white prime minister. The party holds all 20 white parliamentary seats.

That remark apparently had special meaning to some of his audience since there are reports that several parliamentary members of Smith's party plan to quit soon and become independents, thus opening the way for white appointments to the Cabinet.

Mugabe also made conditional offers to the whites in other areas but gave no ground. The government, he said, is "not talking of nationalization . . . unless the force of circumstances obliges us to do so."

Referring to about a dozen whites jailed under emergency regulations, he said the intention was for all to come to trial.