Ka cika wannan jumla: Zebley ya kasance wakili na musamman na FBI yana aiki da sashen yaki da ta'addanci na hukumar na tsawon shekaru bakwai. A matsayinsa na wakilin FBI, Zebley ya binciki al-Qaeda
hare-haren bam na ofisoshin jakadancin Amurka a gabashin Afirka a 1998, kuma bayan hare-haren 11 ga Satumba an sanya shi ga ƙungiyar FBI ta PENTTBOM, wanda ke binciken 'yan ta'addan da ke da alhakin hare-haren. Zebley yana cikin tawagar da ta kama daya daga cikin 'yan kunar bakin wake na ofishin jakadancin, Khalfan Khamis Mohamed, a watan Oktoba 1999 a Cape Town, Afirka ta Kudu. Zebley na ɗaya daga cikin masu binciken da suka gina shari'ar a kan Zacarias Moussaoui, wanda a ƙarshe aka yanke masa hukuncin ɗaurin rai da rai. Zebley ya kasance mai ba da shaida a cikin hukuncin hukuncin Moussaoui, yana ba da shaida game da hanyoyin da furcin Moussaoui a cikin 2005 zai iya taimakawa wajen bin diddigin satar jirgin 11 ga Satumba a cikin watan kafin hare-haren idan ya ba da gaskiya lokacin da aka kama shi.