In general, as long as you have the proper PCIe 6/8-pin connectors you're fine. It's almost certain your PSU does.
I'm not certain, but I think the GTX660 requires 2x6-pin connectors though some cards may need only a single 1x8-pin.
*Are you getting a good DEAL on that Zotac?
I ask because you can get a better GTX760 for $240 with two games. I'm not sure what you're paying for that card.
http://www.techpowerup.com/reviews/ASUS/GeForce_GTX_760_Direct_Cu_II_OC/27.html
**The GAMES seem not to be listed in all stores. At Newegg ($240 after $10 MIR) they are:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121775&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-Video%20Card%20-%20Nvidia-_-ASUS-_-14121775&cm_sp=&AID=10440897&PID=3938566&SID=
Games are:
1) Assassin's Creed 4, and
2) Splinter Cell Blacklist