General

On the third hit for giga crash you can already tag team back to Alpha, so don't rely on the animation finishing for the last hit and just spam your wind cutter as soon as you see Beta jump up to smash back down

For single target dps;
Wind cutter - Rolling cross - Spin driver (as soon as rolling cross in tag is casted) - Giga Crash
Then go back to the first cycle.

This is the best dps cycle as far as I know

Zeros are too much work. Shutouts to Spammy classes <3

Thanks.
Geez, all classes I play pretty much, I only use 2 skills ever. So I doubt I'll get used to Zero's style so I'll just leave it at wind cutter and giga crash for everything, lol.

I do that same combo on C/Zakum o.o
Incase you meant you were confused at the numbers:

(Alpha) 1 = Moon strike, 2 = Flash Assault, 3 = Rolling Cross, 4 = Wind Cutter
(Beta) 1 = Rising Slash, 2 = Flash Cut, 3 = Spin Driver, 4 = Giga Crash

I think the ideal combo depends on the situation, you're either going to want one that just allows most time spent in tag mode, or as much tagging time with some dodging ability. Making sure the combo also gives the most dmg output while balancing all the previous goes without saying. Though it was just said...
Just a guess, IANAExpert on Zero.

I guess you can watch some bossing videos to get an idea of what to do (like this, [url=https://www.youtube.com/watch?v=xPpM7FnXpp8]BOSS[/url]. )
From what little I read, I think [url=http://www.basilmarket.com/user/azurespirit]this user[/url]is a good bosser to watch.

P.S. If you're using youtube, you can slow down the speed (available in the settings button, shaped like a gear below the video) , to be able to see what's happening, as Zero has a lot of flashy animation in it's moves.