I like Zack Martin ... but as an NFL OT I think he will be solid, not spectacular. It is as an OG where I think he can become truly elite. His footwork, power, flexibility, hands, all the little things are right. The guy might be the next Logan Mankins. He is a great fit for a ZBS.
But, as an NFL OT, I think he lacks length. With short arms and narrow shoulders I don't really see the extension he would need to play LT, and would prefer to play RT. When you're lining up against long super-athletes like Aldon Smith (unbelievably long arms), JPP, and in our own division guys like Mario Williams and Chandler Jones, it is going to be very difficult to continually stonewall those guys when they always get leverage on you. Let's face it, the competition at the Senior Bowl isn't that stiff. Trent Murphy is a decent player, but he is subpar compared to most NFL starting RDE's and ROLB's. As a LT, I think ZM might be a bit overmatched despite his strength being working in space.
As an OG, his only issue may be power. Despite his good knee bend and leverage, he is more of a move guy than a powerhouse.
While I would welcome him and be happy to draft him at 19, if Taylor Lewan is also there I'd take Lewan 10 out of 10 times. He isn't as quick as Zack is, but those long levers really help in pass protection. But if the OT's are gone and we can get an elite LG like Martin, I'd be quite happy to have him.