Pavol Kutaj

Adding my two cents here: 

1. Paste your code as plain text into a Google Doc. 
2. Use Code Blocks add-on to do the syntax highlighting.
3. Import the Google Doc into Zendesk using the import tool.
4. Copy the code into an article. 

Advantage: The code is both highlighted and can be copied and pasted. 
Disadvantage: Time, of course. But you can import in batches or you can have plenty of snippets in a single Google doc and then just distribute snippets in your articles. Also, at least basic HTML knowledge is needed, the import tool is now that seamless. 

Cheers!