When reporting a zero conditional, the following tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. changes may be applied.

In this type of mixed conditional the if-clauseA group of related words containing a subject and a verb. is in the second, while the main clauseA clause that could be a sentence in itself. E.g.: I wouldn’t go there if I were you. ("I wouldn't go there") When I arrived he was surfing. ("he was surfing") is in the third conditional.

If Mr Douglas had a moustache, Ms Zeta Jones would probably not have married him.
If I were smarter, I would have been able to answer.

Compare:

The difference between the zero and the first conditional is that while the zero conditional expresses a general present or past situation, the first conditional refers to a specific future eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head..

if-clause with past simple or continuous
main clause with past simple or continuous

If we weren’t in the mood, we didn’t talk to each other for hours.
She walked the streets without an umbrella if it was raining.
If she was sad, she just stared into the distance without saying a word.

if-clause with present simple or continuous
main clause with present simple or continuous

If I stay up until 3 in the morning, I am totally exhausted the next day.
If he is cursing, it means that he is very angry.

This use of the present simple tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. is similar to what is often explained with the phrase general truth. This term covers facts which are always true or eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head.s which always happen.

The Earth revolves around the Sun.
"Boys don't cry."

The zero conditional does not imply a real condition, but rather it expresses that something is or was always true. Here the linking wordA part of speech connecting words, clauses or sentences. E.g.: Although everyone but Julie heard the news, no one seemed to care. ("although", "but") if means when. Note that in the other conditional sentences we cannot replace if with when.