This is a limitation of the ZIP file format.  There is no provision
in ZIP for a "timezone" field.  There is only a date and time field (in the
old MSDOS format).  Fossil inserts the date and time as UTC.  If the program
that unpacks the ZIP archive interprets the time in the local timezone, then the
time can be off by several hours.

I cannot think of a reasonable workaround.  Can anybody else suggest something?