This is probably two diff. questions (one more of an MS question) and
then how it relates to ZEN.

If using MS Group Policies via ZENworks, what exact order do they get

By that I mean:

PC is turned on and sits at the CTRL-ALT-DEL login prompt.

Does a "workstation" policy get applied then?

and then at login, does the "user" policy get applied?

And of course in ZENWorks, you can apply a GPO via a ZEN workstation
policy or a ZEN user policy. What does this do?

The reason I ask is that we're experimenting with GPO on Windows XP.

We first tried in AD by applying a GPO to a specific AD Workstation

It seemed that it took 2 reboots of the workstation for the policy to
"kick in".

We then deleted those workstations and the GPO and reghosted the pc's.

Used a ZEN USER policy to deploy a GPO. One of the "workstation"
policies in that GPO supposedly took two reboots as well to "kick in".
Is this normal?

ZEN 6.5 SP1b