First of all, Al Qaeda is anti-Baathist, and secondly, this is not like the situation with Al-Sadr, that told people to attack the US troops.
Al Qaeda has been attacking innocent people as well. So in comparison to the situation with Al Sadr, who did need to be consulted and not ignored, you had someone who felt that the invaders should leave, as compared to someone (Zarqawi) who is also anti-Shia and won't hesitate to kill Shia Muslims (as was the case in Afghanistan).
So my point is that negotiation is most likely something that Zarqawi doesn't want anyways. Sure, ask. Islamic belief dictates that negotiation should always occur during a war. But we all know Islamic Al Qaeda is...
Anyways, I really doubt he would be willing to negotiate, meaning that it is not an option.