Sorry, small differences.

Two different apps that use two different map formats.

Ozi Explorer is one app available for Windows, win ce, and Android. It uses maps in the. Ozi format. You first need to by the app $25 for Android. Then you need to buy the maps and copy them to your device(s). Many types of map available.

Hema maps can be a confusing term. In one sense it is a company that sells maps. You can buy paper Hema maps (eg the Cape York one - pretty good) or the same maps are available in digital, both in Ozi format and for the memory map app.

Hema memory map is an app for both android and iphone/pad. The app is free, and you can download the maps with a free trial. Then you need a 'license' for the maps, which after activation, let's you use the maps. Memory map uses Hema maps.