Prime Minister Abel Muzorewa returned home from the London peace conference today and unofficially launched his reelection campaign at a large airport rally.

A 50-foot banner, draped over the balcony at the airport terminal, proclaimed:

"The winner comes home."

Muzorewa told the crowd that in London he had succeeded in obtaining the promise of an end to British sanctions and world recognition for his country when a British governor arrives to preside during a transitional period leading up to new electins. The elections are part of a British plan to restore the former colony to black rule. It was accepted by black guerrila leaders last week.

The crowd from the black townships was estimated by police to number from 75,000 to 100,000 people, although journalists put its size at 20,000 to 55,000. The turnout demonstrated that Muzorewa has put together an effective, American-style political organization, the United African National Congress. There was disco music on the loudspeakers, prancing majorettes and a uniformed drill team.

"I would say that the Lancaster House conference on Zimbabwe-Rhodesia was a success for our delegatin. It was a victory for democracy and it was triumph for freedom, not only for Zimbabwe-Rhodesia but for the whole free world," Muzorewa told reporters.

"For me, it was an opportunity to fulfill what I had promised the people of this country that elected to power, we would see that sanctions are lifted, that the country was returned to legality and would become acceptable to the international community and that peace would be created once again."

Muzorewa is thought to have created political problems for himself since he took over the government after elections in April. He campaigned on a platform of peace and prosperity. But there has been no peace. Although Muzorewa is the country's first black prime minister, the white minority retained control of much of the government. Thus, the Patriotic Front, Muzorewa's guerrilla opponents, boycotted the election in favor of more war. The rich and extenive farm land ownded by the white minitiry -- roughly half the land in the country -- have not been broken up and redisbributed. Economic conditions in general, are unchanged.

To strengthen his position, Muzorewa's government recently has taken some popular political steps. It announced a freeze on bread prices and price cuts on gasoline, kerosene, sugar and corn, the staple commodity in the black family's diet. It raised the minimum wage for the country's 350,000 black farm laborers from about $16- $20 a month to $27 a month. It appointed a commission to review minimum wages in all industries and come up with higher figures. It released about $13 million in foreign exchange reserves to "create 8,000 new jobs" and to permit the importation of certain "luxuries" for Christmas, including Scotch whisky. It promised pay increases for the bureaucracy and military forces and gave various reassurances to whites on such matters as land expropriation.

Under the agreements reached so far in London, the Patrotic Front alliance between the guerrilla armies of Joshua Nkomo, based in Zambia, and Robert Mugabe, based in Mozambique, has agreed to take part in the coming election. The ballotting is to be carried out under the supervision of a transitional British governor and token forces from several countries of the British Commonwealth.

Muzorewa is outwardly confident of an electoral victory. He was asked today if he could win the coming election.

"Definitely," he said.

No one here, except the partisans, claims any knowledge or insights into how the election will go. No public opinion polls are available. Furthermore, the 7 million blacks in the country are dispersed in such a way as to make forecasting impossible.

Where the blacks live and where they work subjects them to varying degrees of influence, pressure and physical intimidation from the contending sides.

Another large and unknown factor is the mater of tribal loyalty.

The Mateble people -- about a million of them in the western third of the country -- are thought to be loyal generally to the their fellow tribesman, Nkomo. The remainder are mainly from the Shona-speaking tribes in central and eastern Zimbabwe-Rhodesia. Both Muzorewa and Mugabe are from these Mashona tribes.

One hundred parliamentary seats are at stake in the election. Twenty are reserved for the white minority, under the proposed new constitution. Muzorewa, Nkomo, Mugabe and several minor parties will contend for the remaining 80. It will take 51 seats to form a government and various forms of a coalition government are possible.

A major question is whether Nkomo and Mugabe would accept an electoral defeat and disband their forces or whether they would respond by continuing the war.