Though it was shown in the book cover with Jerid Messa, he never piloted this machine.
The Doola is a Mobile Armor that appears in the gamebook "Mobile Suit Zeta Gundam: "Jerid Messa's Sortie Order".
The blueprints were made by engineers of the now-defunct Principality Of Zeon.
The design concept shares many similarities with the MA-08 Big Zam. An anti-Federation group got ahold of these plans, revised them and was able to develop a functioning unit.
The final result made it look strikingly similar to "The O". Only the leg parts were different.
The armaments were concealed in the chest area via movable frame armor parts. There were 3 High Mega-Particle Cannons and 6 Anti-air Mega-Particle Cannons. It also has 2 beam saber use manipulators concealed in the abdomen, as well as an I-Field Generator that covers the whole unit.
The hidden manipulators are also reminiscent of The O which was developed by Paptimus Scirocco, but the similarities end there. The leg parts are purely vernier/thruster units, and the back part also has a total of 6 large scale mobility thrusters.
In the gamebook, the Doola served as a trump card of an unnamed anti-EF organization and used it to attack Buckland Base.
At the time, Jerid (considered as the main character of the game book) was assigned to a Federation Ship "Grahf Zepplin" and faces the dangerous MA to defend the base. He is accompanied by Emma Sheen and Kacricon Cacooler.