Why did Commander Zero slip out of Nicaragua?

Nicaragua's most famous living hero, "Commander Zero," has left Nicaragua amid a cloud of mystery. The commander, whose real name is Eden Pastora Gomez, is said to have left a letter implying he was going off to join leftist guerrilla movements elsewhere.

But those close to Mr. Pastora, including family members, deny this and assert vigorously that the popular guerilla leader had strong ideological differences with the Marxist leadership of the Sandinista government.

It is widely believed that Mr. Pastora found it increasingly hard to work in subordinate roles with his fellow Sandinista commanders, many of whom are much less popular than he.

Mr. Pastora is not the only prominent Sandinista to depart. Others who left the country after what appeared to be fallings- out with the top Sandinista rulers are:

* Jose Valdivia Hidalgo, vice-minister of the interior and general director of Telcor, the state telecommunications and postal service, Mr. Valdivia left with Mr. Pastora. Both are now in Panama.

* Fernando Chamorro, a distant cousin of the publishing clan of the same name. Mr. Chamorro was a member of the Sandinista command staff during the height of the struggle between the Sandinista guerrillas and the pro-Somoza National Guard.

Mr. Chamorro left a car dealearship job here and is now in Costa Rica. He had quit the Sandinista movement, but his unexpected departure July 7, only days before the government celebrated its second anniversary in power, has fueled all sorts of speculation -- and is a key topic of conversation throughout the country.

* Edmundo Chamorro -- who left Nicaragua even before his brother Fernando. Edmundo is now living in Costa Rica.

Mr. Pastora has refused comment on his flight last month. Some observers say his widespread continuing popularity may well have made him the subject of considerable envy on the part of his fellow Sandinista commanders. One widely circulated rumor has it that Mr. Pastora, who recently served as vice-minster of defense, fled because his life was threatened by jealous rivals.

Whatever the real reason for his departure, Pastora's absence created a vacuum here -- a vacuum that has grown because of the lack of any explanation of his departure. The government has banned newspaper, radio, and television comment on the issue.

[The opposition newspaper La Prensa was closed for a day last month for using Mr. Pastora's nom de guerre (Commander Zero) in a play on words on its front page.]

[The paper was closed down again July 31 for two days because it allegedly insulted Carlos Fonseca Amador, founder of the Sandinista movement.]

"Commander Zero" gained world attention in August 1978 when he led a guerrilla force that took over the legislative palace in downtown Managua. The move won freedom for two dozen imprisoned Sandinistas.

Later he commanded guerrilla forces in the southern reaches of Nicaragua and became a legend among fellow guerrillas for his brilliance on the battlefield against the well-equipped and well-trained National Guard of dictator Anastasio Somoza Debayle.

The Pastora departure, and the widespread speculation surrounding it, seems more and more an embarrasment to the government.

Mr. Pastora is said to have stopped in Costa Rica to see Edmundo Chamorro -- and to have talked with former Costa Rican President Jose Figueres Ferrer, who staunchly backed Pastora and his Sandinista guerrillas during the height of the fighting in Nicaragua in 1978 and 1979.

Mr. Pastora and Mr. Valdivia both conferred with the late Gen. Omar Torrijos Herrera, Panama's behind-the-scenes strong man who had actively supported the Sandinista movement and was close to Mr. Pastora during the struggle.

When Mr. Pastora secured the release of the imprisoned Sandinistas in August 1978, they all went to Panama. Later during the fighting -- before the May 1979 final offensive against General Somoza began -- Pastora held strategy sessions on Panamanian soil.

"Whatever his future," says Pedro Joaquin Chamorro Barrios, La Prensa's editor, "we have not heard the last of him."

A Sandinista defector, once a field commander for the guerrillas, comments enigmati cally, "He will be back."