Those could have been my hands in the second photo just recently! - although I have been in contact with lots of chemicals I don't regularly come into contact with. We're in the middle of decorating our extension which includes using such things as expanding foam, plaster, coving adhesive, paintbrush cleaner, white spirit, etc etc.
Even with the greatest care in the world it's easy to come into contact with 'trigger' chemicals. Examples, some types of liquid soap will cause my fingers to crack, fuel spillages when filling the car or bus up (petrol and diesel - even wearing those disposable gloves you find at filling statons), washing up liquid, laundry detergent, clearing weeds in the garden, anything with lanolin in it, even some preparations that are designed for 'sensitive skin' can cause me a problem.
I can't comment on the zinc preparation you mention but I did go through a phase of wearing polythene gloves a few years ago with the betnovate I was using at the time - with some good results. Nowadays I just grin and bear it knowing that the symptoms if they arise are usually gone in a couple of days... although I realise not everyone will have that exerience.

Welcome to Skincell btw!

andyb