Use a 'Enable Behaviour' action in an FSM on the object you want to make invisible. In the object field, drag the component of your object on to the action. (e.g. Mesh Renderer, or whatever you're trying to hide). Uncheck the 'enable' checkbox so it's set to disable the component.
On your buttons, when clicked, trigger a Send Event action and set it to Broadcast All. Create an Event (e.g "Hide Object") and click on the left checkbox to make it a global. Set that global event as the event you're sending
On your object you want to make invisible, right click on your action that disables your component and choose Global Transition. Select the one that you created in the step above.
Duplicate the above steps for your other button, but have your Enable Behaviour action 'enable' instead of disable.
So you'll have target object with 1 FSM containing 2 States with a 2 different global transitions going to them. 2 buttons, each with an FSM that detects your click and sends the appropriate event to your object.