Learn Italian: Tutto ciò è strano, ma non è sorprendente. - All that is strange, but it is not surprising.

Ciò is an abstract pronoun meaning 'this' or 'that'. You use it to refer to a general idea, a situation, or a statement just made, rather than a specific physical object. You could use questo or quello here instead, but ciò is very common in written or careful speech when talking about concepts.

Can I say tutto questo or tutto quello instead of tutto ciò?

Yes, you can! Tutto questo (all this) and tutto quello (all that) are perfectly fine and very common in everyday conversation. Tutto ciò is a slightly more elegant way to express the same thing, wrapping 'all of that idea' into one neat phrase.

Why is strano in the masculine singular form if ciò doesn't refer to a specific noun?

Because ciò refers to an abstract, genderless concept, Italian grammar defaults to treating it as masculine singular. Any adjective describing it, like strano, must take the masculine singular -o ending. The adjective sorprendente is also singular, using the -e ending shared by both masculine and feminine words in its adjective group.

Why is there no word for 'it' before the second è?