You are doing a good job connecting the dots, I believe if Zarqawi was in custody the gov't would hold off on announcing if for some time. There have been a lot of leaks from various sources alluding to it though. Then again, I have seen reports that UBL was captured at least 100 times. :)
It is interesting that we got the report of the arrest of the man trying to pass a letter from Zarqawi to UBL. One has to wonder what was in that letter... If he was trying to contact UBL, it was likely something very important (possibly alluding to attacks). The fact that the FBI is so worried about Car/Truck bombs makes me wonder if they had information that Zarqawi helped plan attacks in the US. His specialty seems to be in the area of large car/truck bombs (chem also), he has proven it is a very good technique in Iraq.
It sounds like the Paks have captured two al Qaeda guys that they are refusing to identify until the investigation is completed.
Pakistan Mum on Identities of Recently Arrested, High-Value al-Qaida Targets
ISLAMABAD, Pakistan Aug. 4, 2004
Pakistani officials remained tightlipped about the identities of two high-level al-Qaida terrorists they have arrested in recent days, saying Wednesday that there would be no more information until they complete their investigation.
Interior Minister Faisal Saleh Hayyat announced the arrests of two al-Qaida suspects of African origin one with a multimillion dollar bounty on his head, in an evening news conference Tuesday. He would not name them.
http://www.abcnews.go.com/wire/World/ap20040804_398.html