CDO

I am very new to CDO. I have a longitude/latitude box of data. I need to find the zonal mean for each latitude, concatenate the files for 32 years and split into separate files for each latitude. I know how to do the first two but cannot see if I can split my concatenated files into files for each latitude. The only way I can see is to do a sellonlatbox, setting latitudes to the same value, but will this work as I have already done zonalmean, so will the longitude values be meaningless?

Thanks
Richard Hall