Before asking such questions, make sure you check the following resources:

• See if a similar question hasn't been asked on unmet hours. This question is very similar
• Check the Input Output Reference guide of EnergyPlus. Each object is described, and includes the output variables that are available. If your model has Coil:Cooling:DX:SingleSpeed objects for example, this section is pretty limpid.
• Open the eplusout.rdd after a run... it lists ALL the output variables that are available for you, and doing a search on "Latent" will quickly tell you which one you need. See the answer by Aaron to see how to open it from within the openstudio application on the question I linked above or you can also find it in your file explorer. If your model is called "mymodel.osm" it'll be in mymodel\run\5-EnergyPlus\eplusout.rdd

Now, you won't find this at the zone level, as highlighted in the I/O reference guide here there is no output variable for zone latent load.

You'll find this at the HVAC level. I already showed you which one you need in the case of a Coil:Cooling:DX:SingleSpeed for example, here is the same if you're using ZoneHVAC:IdealLoadsAirSystem