They're epically screwed. Apokolips is the most dangerous planet in DC. Apokolips is a war machine and the center of an empire spanning countless stars. They have the best war tech in the DCU, bar none.
Desaad once showcased all of it in a thread when he battled Quanchi.
http://www.killermovies.com/forums/showthread.php?s=&threadid=473261&highlight=desaad+vs+quanchi
Despite the raw power of all the kryptonians, most of them are fairly inept at using it, having neither experience, instincts, or combat training. They have a core of Zod and a few others, but most are fairly low-level.
I'd expect New Krypton would do well at first, but then the more experienced New Gods would take their tole, the Parademons would just keep coming, and Darksied would shatter their moral by defeating Zod in front of everyone or something like that.