XP1EntFix & XP1DeUTF8
XP1EntFix converts HTML entities to UTF-8, without changing anything else. XP1DeUTF8 does the converse.
Just drop your HTML file on the icon, and Bob’s yer uncle.
You might well wonder why bother? HTML5 likes UTF-8. It’s perfectly good at handling HTML entities too, but I find it easier to edit files I can read...on editors (on the other platform) that display UTF-8...on the other hand, whatever platform I’m using, it’s easier to type ą than to remember (or look up) some arcane code for it. Even ’ or – are easier to type than however else one gets them.
XP1EntFix leaves ,  ,   and   alone – I prefer to keep those because otherwise they’re indistinguishable from ordinary spaces. There are also a lot of other entities it just doesn’t know about! But it handles most accented and special characters in European Latin alphabet languages or Greek and a motley collection of other items I use – a total of over three hundred entities. It is easily edited to add more as required.
XP1EntFix also converts both decimal and hex number entities to UTF-8.
In Zap (or any editor that doesn't render UTF-8), HTML entities are easier to read than the UTF-8 equivalents... hence DeUTF8...
If any entities or UTF-8 characters are unknown to EntFix or DeUTF8, they’re left unchanged, and a log file is generated listing them.
(They’re self-extracting archives, so all you have to do is download the files into a suitable directory, set the file types to FFC, and double-click on them, which will create the whole applications in the same directory. You can then delete the original downloaded files.)