Flopzillas store ranges in a txt file (newdefs2.txt/newdefs3.txt depending on the FZ version) which can be imported to GTO+: Settings->Import preflop r... Note 3-step file type switch there.
About hand reviewing, it is not an automated process. Not because it's not possible to just load hand histories, which is also true, but because GTO by default will not mimic your real opponent.
There is a good video about game studying approach with GTO+ on youtube
https://www.youtube.com/watch?v=Xn3u7DBZNWA
