Hi Jake, I agree.
Kribs and rams both like to stay toward the bottom. They would have overlapping territories and it would not work. Rams can be tough too, but the kribs will get bigger. One or the other would do fine, but both will not work. Not even a little. Forget successful breeding, they'd probably harass each other to death. If you did only one or the other I think you would have success breeding them.
If that's your goal, get ottos or BN plecos as algae eaters, neither will eat fry.
The zebra danios will stay up top, and will coexist nicely with one pair or the other. They will eat fry if given the chance.