Paint help for bathroom cladding please

Hoploz

I've put pre-primed, moisture-resistant mdf butt & bead sheets on my bathroom walls and I'm not sure how to paint it.

I've got a water based Crown satin paint for top coating, but do I need to undercoat the pre-primed mdf first?

I've got a Zinsser undercoat which is oil based ... Can I use this under a water based top coat? I've read you shouldn't use water based and oil based together.

Any advice welcome please as I'm ready to start but can't decide!

Hoploz

... Well no help here then!

I read too many horror stories online of people having problems getting water based paint to adhere to oil based undercoat, so I decided to just go straight on with the satin at 5 o'clock this morning to avoid the heat!

One coat done and it needs another, but looks to have taken fine to the pre-primed boards.