The current rebellion in Zaire's mineral-rich Shaba province is only the latest episode in a bitter struggle between President Mobutu Sese Seko's pro-Western government and the Soviet and Cuban-backed government of Angolan leader Agost Inho Neto. It is a struggle that has been going on since the 1975 Angolan civil war.

The latest flare-up, however, comes at a time of intense Western, and particularly American, concern about expanding Soviet-Cuban activities throughout Africa. In this context the possible fall of Mobutu and his replacement by a pro-Soviet leader must take on special meaning for both Washington and Moscow.

The issue at stake at once simple and complex: Can the Carter administration sit by and risk the overthrow of Mobutu when the prospect, although still very far from clear, is a likely new leadership in Zaire supported by Angola, Cuba and the Soviet Union.

Direct U.S. intervention, however, even to rescue Americans being held by rebels, could involve as many risks as standing by and letting events take their course. Among other things, it would tend to commit the administration to the defense of a government already in serious economic and political trouble and possibly spell the end of its new Africa policy based in part on non-intervention in the internal affairs at black Africa.

This dilemma would be resolved if a successful counter offensive is mounted by the Zairian Army, acting on its own to retake Kolwizi. It appears from preliminary accounts that the army is fighting far better than during last year's Shaba crisis but the Katangese rebels are also apparently better armed and organized.

The roots of the Angolan-Zairian feud date back to the struggle for power among Angolan nationalist factions at the time of Portugal's withdrawal from its most prosperious and developed African colony in 1975.

The struggle became public and increasingly bloody in early 1974 and involved three groups: the Popular Movement for the Liberation of Angola, Marrist-oriented and supported throughtout the anticolonial war by Cuba the Soviet Union and various socialist African states, the National Fron for the Liberation of Angola, backed principally by Zaire and aided overtly or govertly over the years by such diverse powers as China. North Korea and the United States; and the National Union for the Total Independence of Angola (UNITA), whose backers included various Western and moderate African states and eventually South Africa.

By the end of the civil war in early 1976, Zaire had troops and heavy weapons inside northern Angola bolstering the National Front, South Africa had several thousand soldiers in southern Angola helping UNITA and National Front forces there, and Cuba had deployed 15,000 to 20,000 combat troops and advisers supporting the eventually victorious popular movement.

The Soviet Union sent $500 million in arms to the Popular Movement while the United States, through the Central Intelligency Agency, provided UNITA and the National Front with $25 million to $30 million in arms through Zaire and South Africa.

If the massive Soviet-Cuban intervention clearly was the decisive factor in the Popular Movement's victory, it was no less true that Mobutu's former enemies - exiled gendarmes, or police, from the former secessionist province of Katanga (now Shaba) - played a role in helping the Popular Movement establish its control over northeastern Angola.

In the course of the Zairian leader's own rise to power in November 1965, and the crushing of the Katanga secessionist movement, thousands of katangese gendarmes were killed, executed or massacred by troops loyal to Mobutu. Those were the seeds for today's internal Zairian blood feud.

With the establishment of a popular movement government in Angola after its victory in March 1976, the Katangese began organizing a new force of several thousand guerrillas in camps located in northeastern Angola adjacent to Zaire's Shaba Province. It seems that dissident Lunda and Baluba tribesmen provided most of the recruits and the katangese gendarmes the officers.

The extent of Cuban and Soviet assistance to the new force - knwon as the National Congo Liberation Front - has never been clearly established, Western correspondents who covered the first Katangese attempts to capture Shaba Province in March and April of last year were not impressed by the motley array of captured NATO. Soviet and homemade weapons put on display by the Zaire government. Conspicuously absent were any sophisticated Soviet weapons.

Meanwhile Zaire was engaged in helping the Popular Movement's enemies.

Prior to both outbursts of fighting in Shaba, the Angolan government reported a sharp increase in national fron activities in northern Angola and charged Zaire with abetting the rebirths of serious guerrilla warfare there.

Late last year, the Angolan government announced that the national front had attacked by land and sea at Ambriz, site of one of its old military headquarters during the 1975-'76 civil war in northern Angola. Then, in March, Angola said its Cuban-supported army had repulsed "a strong Zairian military contingent," backed by planes and helicopters, that had crossed the border and seized the town of Calanda in the Carambo in area.

Exactly what took place in these two incidents has never been confirmed by any independent outside source. But the fact that the national front has taken several Western journalists on trips into northern Angola recently and that the British Foreign Office in January publicly warned its nationals about a new effort to recruit mercenaries strongly suggests that anti-Neto guerrillas are again active and that Zaire is allowing them to operate from its territory.

The available evidence seems to indicate that the Mobutu and Neto governments, both heavily dependent on foreign assistance for their survival, are very much locked in a deadly struggle by proxies in a bid to do each other in - with serious implications in the revied East-West cold war and over black Africa and for the standing and prestige of both the Soviet Union and the United States.