I have an excellent tip for anyone trying to remove the cutting height dial ("cam dial") from a ZD326 mower in order to get the control panel off. I think the ZD331 has the same parts, based on what I've read.
When you remove the front portion of the control panel, which is independent of the main panel, you get access to a clevis pin on the cutting height dial shaft. This pin is the only thing that holds the shaft in the mower. You turn the dial so you have access to the pin, and then you pull it out with long pliers. Getting the pin back in is probably no fun at all, but the dial is not made to slip off easily, regardless of what anyone says, and I learned it is very easy to break.
Applying heat to the dial doesn't work because it's impossible. That's the main problem with that method.
When you remove the front portion of the control panel, which is independent of the main panel, you get access to a clevis pin on the cutting height dial shaft. This pin is the only thing that holds the shaft in the mower. You turn the dial so you have access to the pin, and then you pull it out with long pliers. Getting the pin back in is probably no fun at all, but the dial is not made to slip off easily, regardless of what anyone says, and I learned it is very easy to break.
Applying heat to the dial doesn't work because it's impossible. That's the main problem with that method.