While Zaire presents itself in its press communiques and briefings as bombing its ground bravely, intelligence reports reaching European capitals say Zaire's army is crumbling rapidly.

The gap is so wide between the optimistic assessments given reporters in Zaire and the scarce hard information picked up by intelligence progressionals that at times there appear to be two armies fighting - or, more to the point, not fighting - under the command of President Mobutu Seae Seko in Shaba Province, formerly Katanga.

The army of the official communiques is a predictably valiant, cool headed force, launching air attacks on the Katangan invaders and retaking caputred villages.

The Zaire army depicted by intelligence reports from sources sympathetic to Mobutu, however, bears more resemblance to the panic stricken, undisciplined mobs that passed for Congolese army units in the early 1960s. They flee rather than fight.

"We have no idea if there are Cubans with the invaders or not," one Western official in another capital said with exasperation as he sifted through intelligence reports earlier this week. According to him, "There has been absolutely no contact yet. There hasn't been a shot fired by a Zaire soldier at the invaders, who are rolling through Zaire like a knife through butter."

Mobutu is said to have ordered his Mirage fighter bombers into the air. They flew in low over Lubumbashi (formerly stanleyville) briefly on March 13, five days after the invasion began, and created such panic that Mobutu ordered the aricraft grounded.

Most of Mobutu's small Italian made Macchi jet fighters are also grounded because of a lack of spare parts. Urgent appeals, to Italy for replacements have not been answered.

The only effective air activity that has been confirmed independently is a few aerial reconnaissance flights made in recent days by the Zaire air force.

The intelligence reports indicate that Zaire's claims of a "bombing and rocket campaign" against rebel strongholds wildly exaggerate the nature of both the attack and the muted response Zaire has made.

On the ground, the picture is even more sobering for those who had expected former sergeant Mobutu to shape up the local armed forces. According to reliable report, he sent one of his regiments south by rail to confront the invaders, but half of the unit disappeared from the train within the first 100 miles of the journey.

Despite American and Belgian suggestions, Mobutu is said to be refusing to commit any significant mumber of his paratroop units, thought to be the only disciplined units in the armed forces, to the south. Evidently trying to make the message clear, the United States included a large number of parachutes in the emergency supplies it airlifted to Zaire this week.

Mobutu appears to trust the loyalty of the paratroopers far more than any other unit, and is apparently afraid to strip himself of their protection even if it would save the south.

"Also, he may fear that they will prove to be no better than the other units, and then he's played his last card," one western official said.