Easy!
Duck like you normally would!
Point your arrow down.
You have to get the mech crank and the motor.
you go in it
The unfinished Mech that Zack was working on is in the garage next to Sully's. You need the Mech Motor and Mech Crank to finish it.In the garage next to sully's shop on the left side of the island.
find the mech crank and mech battery
pound it with the mech's weed whacker
The Mech Walker is the key to entering the storeroom and defeating the monster plants that are active there. Once you finish the Mech with the Motor and Crank, you can attach the Weed Whacker attachment and enter the door at the far left of the island.
You can get the mech crank at living quarters in Zack's room ( go up the ladder and exit the room and walk across the vine and pick up the mech crank)
Go left along the vine and pick up the Mech Crank. Along with the Mech Motor you recovered from the Production Zone, use it to finish building the Mech walker.
Take it to the vine spot and click space bar to cut the vines. (it is to the left)
You cannot, as it will not jump high enough to get to Main Street again. Thus, you cannot get to the blimp.
There are no windows that open inward on Steamworks Island. There is a skylight in the City Hall that can be opened with the Multi-Tool. You go out the hatch above Zack's room in the living quarters, to reach the Mech Crank on the vines.
You cut the weeds blocking the door of the Storeroom far left of the island) with the Weed Whacker. The weed whacker is in Captain Ziggs' room atop the Hub, and must be attached to the Mech Walker (in the garage next to Sully's). Finishing the Mech requires the Mech Motor and Mech Crank.