Flash Ignite are the best summoner spells for Zed if your looking to get a bang for your buck. You may go Flash and Exhaust as well but I highly recommend Ignite and Flash.

Zed's combo is very limited but it has an insane amount of burst. The main combos I use are W,E,Q. and W,Q.E. Typically if you want to do as much damage as possible with those combos you wanna hit them with the Q, don't hit any minions and them for that will negate some of your Q damage because your hitting something else, not just the champion itself. For the ult combo I usually just do the same thing. Start of with yoummus for the speed boost, then use your blade of the ruined king active, ignite and follow the combo: R, W beside or behind them depending on the situation I'm in and who I'm laning against then follow up with a E - Q or Q - E.

There are several mastery options viable for Zed. 18-12 and 12-18 are the most common and best.
The listed links are the current mastery options and other viable ones.

Current: http://imgur.com/Hoac6RY
Other Viable Option: http://imgur.com/D5Qwvgu
Last Option: http://imgur.com/xVFd1kp

There are other options as well, however these are the main ones I use and have tested several games on and had the most success with.

Overall Zed is a fairly decent midlaner. I find him to be the funnest assassin as well. He does have huge outplay potential too. The only problem I find with Zed is he doesn't seem to fit with team comps, unless YOU have a very heavy lock down team comp, for example: Lissandra - Top, Vi - Jungle, Zed - Middle, ADC - Lucian / Miss Fortune, and Support - Thresh / Nautilus. Usually your going around picking someone off then grouping or split pushing all game. He can be VERY effective if put in the right hands. If you want to master him I recommend playing him a lot and I mean a lot, it's not just going to happen. Your not just going to become Faker. Anyways that's a wrap for my first guide, I hope this helped you out in any way, shape, or form.