I would be okay with using the Zinnser 123 (the latex version) to prime oil based trim. If you are painting flat over flat on the walls, there really is no reason to spot prime. In fact, it is really not recommended because those spot primed areas could flash through the flat paint layer. If you really want to spot prime, then use the flat paint itself, not an actual primer. I still haven't found a water based clear coat that I like. You need to apply 3-5 coats with sanding in between to get the wood smooth and I only want to apply two coats and be done. So, this depends on how picky you are and how much time you want to spend sanding and applying successive coats. I prefer and oil based sanding sealer followed by a coat of oil based poly or varnish.

Thank you for your response.

I will definitely use the 123 and make sure that the painter sands all the doors. The Zinsser website shows the 123 and 123 plus, both acrylic based. I've only seen and bought the regular 123. I'm not sure which one is the latex version.

I actually bought some Defthane for the clear coat, but the painter thinks that oil based clear coat would make the wood yellow over time, with a bubbly or porous appearance. Do you have a brand for the sanding sealer and oil base poly that you like?

Yea when I say latex version, I really mean acrylic. Oil based poly will yellow over time it's true. I like Minwax.