In history, the battle of Manzikert was won by the Seljuk Turks who have managed to establish a foothold in Anatolia. In our history, the situation was much different.
To begin with, the Seljuk did not have to face a Byzantine army, because the Byzantines no longer existed as any significant entity by 1006 A.D, and only had control of the area around Constantinople. All they had to face was garrisons in that city, but even then their army supply was severely limited due to their failure to capture any city in Anatolia or Iraq:
In fact, in our history, all the Seljuks managed to do is form foraging expeditions, raiding parties and encampments all over the desert regions of the Middle East:
Siege of Constantinople, 1078 A.D:
The Seljuk armies were skilled at travelling in mountainous regions and at one point had the city of Anqarah cornered from the East and West:
Alp Arslan was with the Western flank. Seeing imminent defeat, Arslan decided to instead head West and try to take Constantinople, aware that garrisons are few. However, Arslan underestimated the nearly impenetrable walls:
His army consisted of his main force combined with some Buddhists who were promised the "Liberation of Anqarah". They planned to take Constantinople first and then return to take Anqarah and free it from the hands of the Muslims.
The city of Constaninople managed to defeat the Seljuk army, but is now severely weakened:
Is this an open opportunity for the Ummah?