As he has done so often in the six years since seizing power, Pakistani President Mohammed Zia ul-Haq again has outflanked his vocal but largely ineffective opposition, leaving it in confusion and disarray after his latest promises to hold democratic elections and end the country's martial law by March 1985.

Despite protests that have resulted in the arrests of hundreds of opposition leaders, Zia has emerged from his "power-sharing" announcement earlier this month with a tighter hold on power.

Police fired upon demonstrators attempting to free prisoners from jail Saturday at Khaipur Nathan Shah in Sind Province, Reuter reported, and two protesters were wounded. Official sources said that 12 persons have been killed in seven days of demonstrations.

Zia appears to be in a position to consolidate his control further by moving to a stronger presidency based on the Turkish model of a central role for the military in a controlled democracy.

Barring the kind of mass movement that toppled Gen. Mohammed Ayub Khan's military regime in 1969, Zia appears uniquely positioned to construct during the next 18 months the kind of tightly managed Islamic democracy with a military tinge that has gradually taken shape in his vision since the Army coup d'etat through which he ended the turbulent administration of Zulfiqar Ali Bhutto on July 5, 1977.

Zia has largely neutralized the militant opposition by jailing its leaders and manipulating it into infighting. He has deflated moderate dissent by tantalizing it with political reform, placated disgruntled elements in his Army with the promise of letting them get out of the government and return to the barracks, and has offered the nonvocal majority a choice between continued economic and political stability under a disciplined government or partisan chaos in the streets.

Even here in Karachi, the capital of Sind Province and traditionally a cauldron of dissent, Zia has won the grudging respect of opposition leaders for his adroitness in manipulating the eight-party Movement for the Restoration of Democracy into a position of virtual impotence.

"He has played us like a good conductor plays an orchestra," said Shahida Jamil, a Karachi lawyer and activist in the banned Tehrik Istiolal Party founded by the former Air Force chief of staff, Air Marshal Mohammed Asqhar Khan.

Some opposition leaders say they believe that Zia's intelligence operatives have penetrated the opposition alliance and suspect that the president is satisfied to keep the quarreling Restoration of Democracy Movement as it is to prevent the emergence of any unified opposition party.

The most recent debacle in the opposition coalition occurred earlier this month when the executed Bhutto's banned Pakistan People's Party said it would not go along with a planned boycott of partyless local council elections, then reversed itself amid a furor within the party.

The Pakistan People's Party, nominally headed by Bhutto's widow Nusrat and daughter Benazir, remains the most articulate and popular political party in Pakistan. But it has suffered from a lack of direction, with Nusrat Bhutto appearing bent on pursuing the politics of revenge, Benazir Bhutto pursuing social change, and Ghulam Mustafa Jatoi, the party leader whose power lies with rural landlords, concentrating on organization.

Although Jatoi was arrested for leading an anti-Zia protest on Pakistan's independence day, he is perceived by other opposition leaders as an unwitting object of Zia's manipulation of the Restoration of Democracy Movement.

Indeed, a gathering of more than 10,000 protesters last Sunday at the tomb of Pakistan's founder, Mohammed Ali Jinnah, appeared to be stage-managed not only by the Restoration of Democracy Movement, but also by the security forces.

Stick-wielding Zia supporters, who an hour earlier had attacked a group of protesting lawyers at the tomb, melted away as if on cue when Jatoi and several other opposition leaders who had evaded an overnight police manhunt made a dramatic appearance. As the crowd roared its support of the leaders, a cordon of security forces at the street entrance parted for the procession, and, after an hour of speeches calling for removing Zia from power, allowed the leaders to leave unmolested.

But the next day, when Jatoi and Mairaj Mohammed Khan, president of the banned National Liberation Front, appeared at a downtown rally, they immediately were arrested.

Although hundreds of opposition leaders are under arrest, Zia points out that most are merely confined to their homes. He notes that censorship is applied relatively lightly to the press, dissidents are allowed to let off steam in letters and guest columns, while political meetings, although banned, often are winked at by the authorities.

Conversations with Pakistanis not actively involved in politics reveal a belief that a mass protest movement would only lead to an overthrow of Zia by another military junta and yet another cycle of instability and repression.

Another theme that frequently arises in conversations with Pakistanis is that while martial law, on the face of it, may be odious, the memories of political excesses and abuse of power by some democratically elected leaders, including Bhutto, are still vivid. For Pakistan's business community, the economic and political chaos that often accompanied democratic leadership is a painful memory.

At the moment, Zia also appears to be comfortably in control of his armed forces and general staff.

There are elements in the armed forces that feel uncomfortable with martial law and would like to "go back to the barracks," as military sources put it, but Zia has kept their uneasiness under control and transferred or retired the most outspoken dissenters. Some officers are said to worry that the image of the armed forces will be damaged by corruption and abuse of power.

But with the United States embarked on a $3.2 billion military and economic aid package to shore up Pakistan as a front-line state against Soviet expansionism, and with a national budget heavily weighted in favor of the military, the well-disciplined armed forces probably are more content now than ever before, political observers say.

Additionally, the Soviet occupation of Afghanistan has aided Zia, transforming him into the leader of a strategically important state and an internationally supported haven for 3 million Afghan refugees. All of this has deflected attention here and abroad from his sluggishness in restoring democracy.

Zia also has capitalized on good weather, bumper crops and on the growing hard currency remittances from migrant Pakistani workers, all of which are helping his sagging economy.

His promise in a televised speech on Aug. 12 to hold national and provincial elections by March 1985 was not the first such promise by Zia. When he overthrew Bhutto in 1977 he promised to hold elections within three months and since has frequently made similar promises.

It still is unclear just what changes Zia has in mind for Pakistan's political system. He has said the 1973 constitution, suspended when he seized power, will be restored, but only after being amended to create a position of prime minister, with whom the president would share governing duties, and at the same time strengthening the president by empowering him to dismiss the prime minister and dissolve the National Assembly.

In the promised elections, he has not said whether political parties will be allowed to participate or whether former candidates of the banned parties may run.

Zia also said that Pakistan will have a strong national security council to assist the president "at the time of need," but he has not specified what role the military will play in the government.