There are endless protocols and methods which embed ipv4 addresses to ipv6 ones. RFC 4291 specifies exactly what you want, all-zero prefix+ipv4 address: https://www.rfc-editor.org/rfc/rfc4291.html#section-2.5.5

See also the text representation section: https://www.rfc-editor.org/rfc/rfc4291.html#section-2.2

   3. An alternative form that is sometimes more convenient when dealing
      with a mixed environment of IPv4 and IPv6 nodes is
      x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of
      the six high-order 16-bit pieces of the address, and the 'd's are

      the decimal values of the four low-order 8-bit pieces of the
      address (standard IPv4 representation).  Examples:

         0:0:0:0:0:0:13.1.68.3

         0:0:0:0:0:FFFF:129.144.52.38

      or in compressed form:

         ::13.1.68.3

         ::FFFF:129.144.52.38

So in addition to having the addresses embedded on binary level, you even have that text notation that uses traditional ipv4 dot-notation!

You might ask why they are not more prevalent, but then you will find the practical issues that various transition mechanisms are attempting to solve.