This Zain Al-Abedin Hasan is not unknown. He is presumably the same as the "ZAIVAL ABIDEEN MUHAMMAD ASAN," a.k.a. "ABU ZUBAIDA," who appears in the
AUTO DE PROCESAMIENTO (INDICTMENT?) of the Spanish Al Qaeda cell issued by the court in Madrid on Nov. 18, 2001. According to that court document, Abu Zubaida was already a high-ranking official of Al Qaeda in 1997, when he took over the placing into training camps in Afghanistan of recruits coming from Al Qaeda cells like the one in Spain all over the world.
Here's confirmation of the role of Abu Zubaida (the nom de guerre of this Palestinian) in heading Al Qaeda's camps, from a
NY Times article from back in July on the trial of Ahmed Ressam:
In his testimony, Mr. Ressam said the camps were run by Abu Zubaida, the nom de guerre of a Palestinian whom American officials have identified as an important lieutenant to Mr. bin Laden.
American officials say Abu Zubaida reports directly to Mr. bin Laden and is in charge of recruiting for the camps. Mr. Ressam said Abu Zubaida arranged for his trip from Montreal to Afghanistan, providing him with Afghan clothes and an Afghan guide to take him from Pakistan to a camp called Khalden.