For the record (in case you're new to this particular series of cross-promotions), this Empires & Allies promotion requires that you play Zynga Slingo on Facebook and earn at least 30 Medals by playing its combination of bingo and slots. When you've reached that total (which might take you a couple of days to do), you'll be able to come back to your empire in Empires & Allies and will be given a set of boosts for future use.
To be specific, you'll receive a Tactical Nuke for dropping on strong enemies, a battery worth 15 energy points and a pack of 15 Element Z. These items may not have a huge effect on your game in the long run, but they're free, so we really can't complain (plus, watching a Nuke destroy enemy units is oh-so-fun).
What do you think of this Empires & Allies cross-promotion? Have you already completed the steps necessary to earn these free items, or will you have to go play Zynga Slingo some more to earn them? Sound off in the comments.