You need to give us more info.
1) How fast is it at the moment?
2) How fast do you want it?
3) Are the job, Redshift and mysql in the same environment or does the data have to cross the internet?
4) Are indexes (in MySQL) used? Can they be switched off for the load?
You say you want 75,000,000 rows to be processed in minutes. You do realise that for this to be done in 1 hour (for example) would require 20833 rows per second. While that is certainly not unachievable, it would still be hard in an hour using a single MySQL instance in a remote location to the Redshift box and the job.