Nearly every possible Zapdos set is in the analysis...except for Choice Scarf Zapdos, which Jrrrrrr showed certainly is viable, going so far as to say "In all of my D/P experience, this is the best lead I have used." (here is his team: http://www.smogon.com/forums/showthread.php?t=40713)
Anyway, the set:
http://www.smogon.com/dp/pokemon/zapdos
[SET]
Name: Choice Scarf Zapdos
Move 1: Thunderbolt
Move 2: Hidden Power Ice / Hidden Power Grass
Move 3: U-turn
Move 4: Thunder Wave / Toxic / Drill Peck / Roost
Item: Choice Scarf
EVs: 4 HP / 252 SpA / 252 Spe
Nature: Timid / Modest
[SET COMMENTS]
<p>Choice Scarf Zapdos is meant to lead, and is meant to give issues to common leads like Gyarados, Salamence, Gengar, Yanmega and Ninjask (if they decide not to Protect first turn). If the opposing lead is not a great match up, Zapdos can U-turn away to the appropriate counter.</p>
<p>Hidden Power Ice is chosen because it complements the Electric STAB well, and it is Super Effective against Garchomp. If defeating Swampert, Rhyperior and Gastrodon is of absolute importance, Hidden Power Grass can be chosen in this slot as well. The last slot's move comes down to which is more important: debilitating Infernape and Gengar with Thunder Wave, or crippling Swampert and Hippowdon with Toxic. If Heracross or Breloom are significant issues, Drill Peck can be considered. Finally, Roost is also a viable option over either status move and Drill Peck, if only to prevent Stealth Rock from hindering Zapdos' switching capabilities.</p>
<p>Zapdos is Timid because it helps it outspeed Adamant Choice Scarf Garchomp, Modest Choice Scarf Gengar and nearly all versions of Deoxys-S, besides the ones with a +Speed nature and heavy Speed EV investment. However, Modest becomes a viable option if OHKOing Garchomp everytime is desired, or if dealing more general damage to Gengar and Infernape is desired. Modest can also be chosen if it is felt that Timid is not helping Zapdos outspeed threats like Timid Choice Scarf Gengar or if high Speed Deoxys-S become popular.</p>
Anyway, the set:
http://www.smogon.com/dp/pokemon/zapdos
[SET]
Name: Choice Scarf Zapdos
Move 1: Thunderbolt
Move 2: Hidden Power Ice / Hidden Power Grass
Move 3: U-turn
Move 4: Thunder Wave / Toxic / Drill Peck / Roost
Item: Choice Scarf
EVs: 4 HP / 252 SpA / 252 Spe
Nature: Timid / Modest
[SET COMMENTS]
<p>Choice Scarf Zapdos is meant to lead, and is meant to give issues to common leads like Gyarados, Salamence, Gengar, Yanmega and Ninjask (if they decide not to Protect first turn). If the opposing lead is not a great match up, Zapdos can U-turn away to the appropriate counter.</p>
<p>Hidden Power Ice is chosen because it complements the Electric STAB well, and it is Super Effective against Garchomp. If defeating Swampert, Rhyperior and Gastrodon is of absolute importance, Hidden Power Grass can be chosen in this slot as well. The last slot's move comes down to which is more important: debilitating Infernape and Gengar with Thunder Wave, or crippling Swampert and Hippowdon with Toxic. If Heracross or Breloom are significant issues, Drill Peck can be considered. Finally, Roost is also a viable option over either status move and Drill Peck, if only to prevent Stealth Rock from hindering Zapdos' switching capabilities.</p>
<p>Zapdos is Timid because it helps it outspeed Adamant Choice Scarf Garchomp, Modest Choice Scarf Gengar and nearly all versions of Deoxys-S, besides the ones with a +Speed nature and heavy Speed EV investment. However, Modest becomes a viable option if OHKOing Garchomp everytime is desired, or if dealing more general damage to Gengar and Infernape is desired. Modest can also be chosen if it is felt that Timid is not helping Zapdos outspeed threats like Timid Choice Scarf Gengar or if high Speed Deoxys-S become popular.</p>