Typically, even better high-end and mid-range thermal paste, theres very little impact in temperatures (no more than 1-2'c).
The Noctua stuff is pretty good, in my experience - but I've never used that Zalman stuff (I either use NT-H1 or MX-4).
A quick Google search finds this "test"/video:
https://youtu.be/q1sj6dzu5BI?t=39
Showing the Noctua stuff outperforming the Zalman paste by a decent margin, but hardly a controlled environment.
I would use the NT-H1, personally.