I'm sorry that I didn't reply sooner. Starting at version 10.0, there are pseudo-Lo definitions based on the Cape and Hartebeesthoek geographic coordinate systems (datums). One question is what datum this Zimbabwe data is using with the Lo definition. If it's Arc 1950, you would need to define a custom projected coordinate system that has the Lo projection parameters. If it's Cape or Hartebeesthoek, you can use one of the existing definitions, but will then need to reproject the data to Arc 1950 / UTM. There's no direct geographic (datum) transformation between Cape/Hartebeesthoek and Arc 1950. You could use a transformation for Cape or Hartebeesthoek to WGS 1984 and then one between Arc 1950 to WGS 1984 (use #9 for Zimbabwe).