There is a related question here, “Они братья” but “Это упражнения” - why different pronouns?, see my answer there.
In Russian, the English construction
this is / these are are always rendered as
это irrespective of the gender and number of the thing named, the same goes about
it is / they are, if the thing named is non-living:
This is my car. – Это моя машина. (Feminine)
This is my house. – Это мой дом. (Masculine)
This is my window. – Это моё окно. (Neuter)
These are my cars / houses / windows. – Это мои машины / дома / окна. (Plural)
Это inflects according to the gender, number, and case of the following noun only when it is an attribute to that following noun and forms a noun phrase with it:
This car – Эта машина (Feminine)
This house – Этот дом (Masculine)
This window – Это окно. (Neuter)
These cars / houses / windows – Эти машины / дома / окна. (Plural)
But note, these latter are noun phrases, they can function only as elliptical sentences or as parts of a longer complete sentence.