security folks can block zip files that cannot be inspected.
"Questions asking us to break the security of a specific system for you are off-topic unless they demonstrate an understanding of the concepts involved and clearly identify a specific problem."
While there are lots of ways of transferring files, you explicitly asked about sending files via email.
There are lots of ways of sending encrypted messages via email; you have already described one.
The most common solution is to use PGP encryption - that depends on asymmetric encryption - you can publish your public key for anyone to use - but only you can decrypt the messages they send you encrypted with that key. But this depends on both correspondents having PGP software and a keypair which they can use.
There is a variation on this using x509 certificates - but IME it is not as widely used / supported as PGP.
In terms of seting up the trust (exchanging keys) there is some pain, but you only need to do this once.
If you are concerned that your email may be blocked by security because it cannot be inspected, then (although its surprisingly easy to fool such tools) you are attempting to break a security policy and hence your question is off topic.