I don't know of any books that explain this migration ...
I had been involved in a project migrating db2 from aix to zos ..
What version of DB2 are you running on AIX??? If it is 7.2, it will be easier to migrate the applications to Version 8 on ZOS ... The SQL PL and SQL of 7.2 are better compatible with DB2 ZOS V8 ... CTE, Recursion, Sequences, SIGNAL/RESIGNAL etc, are available only on V8 of ZOS .. Nested ATOMIC statements, support for CREATE REPLACE in GTE, IMPORT with INSERT_UPDATE, OLAP Functions etc are not yet available on zOS ... If you have shell scripts, especially with LOAD commands, then there is a lot of rewriting involved to move to ZOS .. Of course, all the housekeeping tasks have to be rewritten for ZOS ....
I will be glad to share my experience if you have any specific questions ...