Secretary of State Cyrus R. Vance will make at least one and possibley two trips to Africa this month, in addition to traveling to Moscow for a major round of nuclear arms control negotiations, officials said yesterday.

That unusually crowded schedule for Vance emerges from President Carter's decision on his African trip to join Great Britain in a new attempt to bridge the angry division between black nationalists over a Rhodesian peace settlement.

There is also a connection between the ferment in Africa and the impending negotiations in Moscow on the strategic arms limitation talks (SALT) Although that is not the reason for the overlapping trips, U.S. officials emphasized, in Moscow Vance will be discussing African issues, in addition to strategic arms control.

The United States, Britain and many African nations fear that a failure to resolve the Rhodesian conflict can lead to a black-on-black civil war between Rhodesain nationalists. That could bring Soviet and Cuban military personnel now in Africa into Rhodesian hostilities.

In the attempt to bring together the feuding "internal" and "external" forces of Rhodesia, Vance and British Foreign Secretary David Owen now plan to meet about April 15 in Dar es Salaam, Tanzania, with leaders of the Patriotic Front.

This is the alliance, led by Joshua Nkomo and Robert Mugabe, that is conducting the guerrilla war against Rhodesia from bases in bordering nations.

As projected by Carter's talks in Lagos with the Nigerian ruller, Lt. Gen. Olusegun Obasanjo, the Dar es Salaam meeting with the Patriotic Front spokesmen and heads of the "frontline" states supporting them is intended to be followed by an "all-parties" meeting bringing together the internal and external Rhodesia forces.

The all-parties meeting is projected for about April 25, at a site still unspecified.

If this second meeting ever comes off, it would include the Patriotic Front leaders plus the members of the new Rhodesian executive council formed last month to produce a subsequent form on black majority rule for Rhodesia: Prime Minister Ian D. Smith and black nationalist leaders Bishop Abel Muzorewa, the Rev. Ndabaningi Sithole and Sen. Jeremial Chirau.

Smith and the three black moderate leaders agreed in Salisbury, Rhodesia, yesterday to give a hearing to Anglo-American envoys on the proposed meeting.

After a three-hour meeting of Rhodesia's transitional government leaders, a spokesman said:

"The executive council would be ready to give consideration to constructive ideas . . . But there could be no question of departing from the Salisbury agreement of March 3, which is already being implemented."

That agreement, which the Patriotic Front has disdained, and which the United States and Britain have termed "inadequate" but a step forward, is designed to lead Rhodesia to black rule by Dec. 31.

Earlier, Bishop Muzorewa and the Rev. Sithole reacted very critically to the Anglo-American proposal. It will start with a visit to Salisbury by the British Foreign Office deputy under-secretary, John Graham, and Stephen Low, the U.S. ambassador to Zambia later this week.

The most derogatory comment came in an attack on President Carter yesterday from Rhodesian Deputy Minister of Information Andre Holland, who charged that Carter is selling out southern Africa's white minorities "for Nigerian oil." Other Salisbury governmental sources said Holland was expressing his own views.

Neverthless, Anglo-American diplomats saw the Salisbury announcement yesterday as an opening. State Department spokesman Hodding Carter said "we are aware of the skepticism that has been offered in Salisbury about our efforts," but "we have been obviously encouraged to proceed with our approach," the Anglo-American plan for a Rhodesian settlement.

Initally, the Patriotic Front leaders, Nkomo and Mugabe, rejected efforts by the United States and Britain to induce them to meet with the internal Rhodesian nationalists, scorning them as "puppets" of Smith.