If you didn't create this file yourself or downloaded it from an unofficial source, . Files ending in .zip that use the names of popular services (like sms-activate.ru) are sometimes used to spread malware. I'd recommend scanning it with an antivirus before opening it.
Option 3: Instructional (Best if it contains a specific tool) sms-activate.ru.zip
"Attached is the archive containing the API documentation and integration scripts we discussed." Option 2: Casual / Direct (Best for a quick share) If you didn't create this file yourself or
Option 1: Technical / Professional (Best for developers or teammates) sms-activate.ru.zip
"Hey, here is the zip file with the resources you needed. Give me a shout once you've had a chance to look through it!"