Install file for Cubase Pro 10.5 corrupted

Ive just purchased Cubase Pro 10.5 …… all appeared to download fine through download assistant … .however when I try to unzip the main 21 gig file It won’t unzip and I get an error.
I have installed the file below now which has set up 10.5 but wondering what i’m missing out on with the big file.

NB downloaded it again with same result

can you advise?