The rapidly shifting currents of African politics will propel Bishop Abel Muzorewa of Rhodesia to Washington this weekend to reinforce efforts by a conservative southern senator to get the U.S. trade embargo against Rhodesia lifted.

Muzorewa's visit, which was swiftly arranged by Sen. Jesse Helms (R-N.C.), underscores a topsy-turvy switch in positions that has occured since Prime Minister Ian Smith agreed in March to bring Muzorewa and two other African nationalist politicians into the top level of a transitional multiracial government.

The timing of Muzorewa's scheduled arrival today compounded the ironies. He will be coming to Washington on a grudgingly granted American visa in the midst of building controversy over the Carter administration's human rights campaign and relations with the Soviet Union.

A few years ago - when he was fighting to keep economic sanctions and world pressure on Smith and the then all-white government - Muzorewa was something of a hero to some Africanists at the State Department. At least one American effort to get him to the United States to present the black nationalist case was thwarted when Smith ordered his passport lifted.

Back then, Helms was devoting more of his time to trying to water down civil rights legislation than inviting foreign black leaders to town.

But the rapidly escalating guerrilla war in Rhodesia and Smith's promise to hand over political power to the black majority this year have helped bring the two men together in Washington. Muzorewa now argues that sanctions should be lifted, and Helms is hoping for victory in the Senate next week on his amendment to the International Security Assistance Act. The amendment would have the effect of restoring American trade with Rhodesia.

Muzorewa's entry into the Rhodesian government assured him of a passport, but caused a brief flurry of discomfort at the State Department yesterday when Helms pushed for a visa for the bishop. Until late last year, American policy had been to refuse visas to members of the Rhodesian government.

The visa policy has been unclear since the transitional government was formed. The State Department officials who considered Muzorewa's application yesterday were aware of reports circulating that Smith may also soon seek to come to the United States to present his case. But after a brief discussion, they approved Muzorewas' application.

A Helms staff member said the senator was not paying for any of Muzorewa's expenses, which evidently will be picked up by the Rhodesian government. In addition to visiting Helms, Muzorewa will have lunch Monday with The Washington Post editorial board.