Your linked article contains this statement:
"The zero conditional (using If you can't...) is often found in old sayings and proverbs."
This is true, it often is, but that doesn't mean it always is. Proverbs are defined as "stating a general truth or piece of advice". Advice isn't the same as an inescapable fact, which a zero conditional statement usually conveys, so don't expect all proverbs to follow that format.
Regarding your specific example - although conditional statements tend to use "if" or "when", there are lots of other ways of phrasing such a statement either omitting or replacing "if". For example:
- Choose a job you love, and you will never have to work a day in your life.
- If you choose a job you love, you will never have to work a day in your life.
- When you choose a job you love, you will never have to work a day in your life.
- As long as you choose a job you love, you will never have to work a day in your life.
- Provided that you choose a job you love, you will never have to work a day in your life.
These all mean the same thing - that if condition [x] is true, it follows that [y] is true.