Painting paper wrapped door frames

Made a big mistake a couple of years ago and bought cheap pre-hung doors at Menards with door frames that are wrapped with some type of glossy white paper over the fake wood frames.
Installed in my cabin but never painted them. Now I would like to finish the project. Menards says sand lightly and prime with Zinser 1-2-3 first.

Any advice?
Anyone else had to paint these fake wood door frames?