I use pkzip25 with no problems:

lccommand="pkzip25.exe -add -max -pass="+m.dtcon+" "+m.filename +" "+ m.efile
Run /7 &lccommand

where:
m.efile= the file(s) to compress ( you can include wildcards: *.dbf )
m.filename= zip name
dtcon= a variable password, I've used the date, the filename or a mixture!

Cheerio