This is written with reference to a ZA (Not "tin top" dash) but should work the same on a ZB.
Removing the dash is as follows
1. Remove all the knobs and switches from their spindles, each octagonal one has a recessed button on the underside of the stem, press the button and pull to remove. The heater controls have a small (hard to replace) screw in a similar position. Leave the two heater controls in the mid position with the heater fan switched off.
2. Take off the instrument panel surround by removing the two long Philips screws on each side of the speedo.The panel is removed by pulling out the bottom first until it just clears the heater controls then carefully slide the top edge out of the main panel. Be very careful with this panel as it is made of laminated plywood and after 50 or so years the glue is becoming very fragile, it is vey easy to delaminate the layers when it is pulled out of the dash.
3. Remove the two vertical windscreen wooden trim strips.
4. The main dash panel is secured by 4 5/16" nuts which are on the lower panel only (none on the top panel). The studs and nuts are one each side of the radio aperture and one at each end in the middle of the last panel.
4. With all of the nuts and washers removed the dash panel including the two end caps will pull towards you until it is clear of the frame
5. Slide it towards the passenger door taking great care of the two short legs on each end of the dash, they are very weak.
5. To get the short leg on the end closest to the drivers door past the steering wheel you can either undo and lower the clamp supporting the steering column or turn the steering wheel until the largest space between the spokes is at about 12 O'clock and rotate the dash to pass the leg through the space. (This may not be necessary in a ZB with the dished steering wheel)
The entire glove box comes off with the dash as does the radio cover, if fitted.
Once the dash panel is removed keep an eye out for a few pieces of carpet or trim material on the top inner panel. These are factory original, fitted to stop the top wooden panel rattling.
Unsurprisingly, fitment is the reverse of removal, apart from an entertaing ten minutes at the end trying to work out which knob fits which switch.
Paddy