The only easy populate plugin I could get to work was EasyPopulate-4.0-master from the github repository.
However there are two strains of EasyPopulate-4.0-master on github that behave differently

And the only way I could I could get it to install was to install it before I installed the other plugin's like FEC.

There are various strains of Easy Populate:
easy_populate_csv_for_zencart_v1.5.x_v1.2.5.7c
Easy Populate with Group Price Per Item
EXCEL Populate..... And maybe others.
These I could not get to install properly.

IMHO They all need to be combined.

I've spent hours sorting through all the problems associated with this plugin(s).