Botrk and ghostblade in conjunction on Zed makes me want to disable shadows.
Pick one or the other, you and your team aren't good enough to finish the game in 30 minutes.
Hydra is perfectly viable, giving more AD and a AD AoE cast. What it lacks is the soft CC botrk provided when chasing after targets. I prefer Hydra always, but botrk is better if there is time to continuously stick to your target.
IMHO, a Botrk + Ghostblade combo is too reliant on autoattacks and once the game gets past 25-30 minutes, there will be less and less timeframes where you can safely DPS the enemy carry. Then, what you need is high burst - provided with raw AD / Crit, with Hydra's AoE cast helping out a bit.
I think a choice between botrk and Hydra is best. It's too expensive to build both and brutalizer should be a must in mid lane, especially for ganking armor-less ADCs.