Once you've neutralized all enemy resistance finish your exploration of the lower deck to find a panel at the zeppelin's beak that controls pods with Mechanized Patriots. Press a button to drop the pods and then attach yourself to the sky-line in order to reach the upper deck.
Start clearing out the second deck of the hangar. Thankfully there aren't too many of Comstock's men here and you can also use the sky-lines to maintain safe distance from them, making them very easy targets. Return to the back of the deck after you've secured the area.
There is a locked gate in the corridor that links the left and the right side of the deck and it leads to Secure Area. Opening the gate is only possible if you have 3 lockpicks.
The cabin located on the other side of the locked gate contains some supplies and weapons. The most important find is Gear #37 located next to a control panel behind an inactive Mechanized Patriot.
Use the stairs to get to an upper deck and you'll find yourself above the room you've explored very recently. Locate a new lockpick on a table between the vending machines.
Go back to the lower deck and start moving towards the zeppelin's beak. There is a locked engineering room opposite the stairs and the lock on the gate can be broken with only one lockpick.
Proceed further into the cabin and you'll find a Voxophone #78 on a table in the second room (under the board). Search the remaining rooms and then resume your journey towards the zeppelin's beak.