What do Zebras sell?

I just found zebras to trade with.

Zebras
Attitude: hostile
Buys: slab (50)
Sells: iron (340 - 368)
plate (2 - 3)
titanium (1 - 1)

I don't really get how it works what Zebra's sell.

Do I get Iron, Plate and Titanium for 50 slab(and obviously the gold/catpower)? Or do I only get 1 of the resources, and is that random?

You will get iron every time, and plates 65% of the time. Titanium is even more rare, and also not a fixed chance. Note that the chances are independent; you can get all three at the same time.

The titanium chance is a base 15%, plus another 0.35% per Trade Ship owned. Also, if the zebras hate you for no reason, the titanium chance is skipped entirely.

In addition to Billy's answer, the amount of titanium you get if you pass the check is 1.5 + 0.03 times the number of Trade Ships.

So, by the time you've reached the 100% mark, you'll have (100-15)/0.35 = 242.857 ships, yielding 8.78 titanium per trade. Of course, you also need 86 tradeposts to prevent the baseless hate :-)