Why is zero plural?

I saw this sentence in the math textbook.

For example, if we choose two 2s, zero 3s, and one 5, we get the divisor

Here they said zero 3s and one 5. Two is plural and one is singular, which is obvious, but zero is considered as plural so they said 'zero 3s'. Why is zero plural?

0 = plural, 1 = singular, 2 = plural, 3 = plural, and so on...

--> This relation does not look natural for me.

That is just how the language works. All numbers except exactly 1 are plural. Note that -1 can also be singular, but that depends on the context and dialect.

Examples

• 0 books
• 0.1 books
• 1.5 books
• 1 book
• -1 book (could also be -1 books)
• 2 books
• 10 books
• -5 books

Please have a look at this answer from English Stack Exchange