I assume the SQL for the query shold look like this.
PARAMETERS Datevar1 DateTime, Datevar2 DateTime;
SELECT AVAILABLECARS.ZONE, AVAILABLECARS.CARCATEGORY, AVAILABLECARS.DAILYRATES, AVAILABLECARS.FROMDATE, AVAILABLECARS.TODATE, CARPICS.CARPICTURE
FROM CARPICS INNER JOIN AvailableCars ON...