Error 2618 Invalid Calculation Division by Zero - response (4) by tclear

Here is the actual SQL:
 
SELECT  I.REPL_GROUP_NBR AS DMDUNIT
 ,'-' AS DMDGROUP
 , 'US_WMT_ST_'||SUBSTR(TRIM(CAST(100000+TRIM(F.STORE_NBR) AS INTEGER)),2,5) AS LOC
 , 'LEW_POS' AS MODEL
 , 'DMDWK' AS DMDCAL
 , 3 AS MODTYPE
 , 'PROJECT STORES' AS DESCR
 , (SELECT MAX(GREGORIAN_DATE)
  FROM US_WM_VM.CALENDAR_DAY
  WHERE GREGORIAN_DATE BETWEEN DATE - 7 AND DATE
  AND SAT_MULT = 1) AS STARTDATE
 , REC_MEAN AS ADJVAL
 , F.STORE_NBR
 , I.DEPT_NBR
 , I.OLD_NBR AS WMT_NBR
 , I.ITEM1_DESC AS ITEM_DESC
 , F.BASE_FCST
 , F.TTL_FCST
 , S.ON_HAND_1_QTY
 , S.MAX_SALE_FLOOR_QTY
 , ZEROIFNULL(P.CK_ST_POS*1.00/NULLIFZERO(S.OPEN_DAYS)) AS AVG_DLY_POS
 , P.CK_ST_POS AS L7D_POS
 , ZEROIFNULL((P.CK_ST_POS*1.00/NULLIFZERO(S.OPEN_DAYS))*7) AS AVG_WKLY_POS 
 , CASE WHEN P.ZONE_STORE = 0 THEN 0 ELSE(P.ZONE_ST_POS*1.00/P.ZONE_STORE)/7 END AS ZN_AVG_DLY_POS
 , CASE WHEN P.ZONE_STORE = 0 THEN 0 ELSE(P.ZONE_ST_POS*1.00/P.ZONE_STORE) END AS ZN_AVG_WKLY_POS 
 , CASE WHEN P.CORP_STORE = 0 THEN 0 ELSE (P.CORP_POS*1.00/P.CORP_STORE)/7 END AS CORP_AVG_DLY_POS
 , CASE WHEN P.CORP_STORE = 0 THEN 0 ELSE (P.CORP_POS*1.00/P.CORP_STORE) END AS CORP_AVG_WKLY_POS 
 , CASE  WHEN AVG_WKLY_POS > F.TTL_FCST THEN 1 ELSE 0 END AS SALES_DIR
 , CASE  WHEN AVG_WKLY_POS > F.TTL_FCST
   THEN CASE  WHEN ZN_AVG_WKLY_POS  > CORP_AVG_WKLY_POS
      THEN ZN_AVG_WKLY_POS 
      ELSE CORP_AVG_WKLY_POS END *1.20
   ELSE CASE  WHEN ZN_AVG_WKLY_POS = 0 THEN CORP_AVG_WKLY_POS
      WHEN ZN_AVG_WKLY_POS  < CORP_AVG_WKLY_POS
      THEN ZN_AVG_WKLY_POS 
      ELSE CORP_AVG_WKLY_POS END *0.80 END AS CZCUR
, CASE  WHEN AVG_WKLY_POS + F.TTL_FCST = 0 THEN CZCUR
  WHEN AVG_WKLY_POS = 0 THEN F.TTL_FCST
  WHEN AVG_WKLY_POS >= F.TTL_FCST THEN
   CASE WHEN CZCUR >= F.TTL_FCST THEN
    CASE WHEN CZCUR >= AVG_WKLY_POS THEN AVG_WKLY_POS
    ELSE CZCUR END
    ELSE AVG_WKLY_POS END
  WHEN AVG_WKLY_POS < F.TTL_FCST THEN
   CASE WHEN CZCUR <  F.TTL_FCST THEN
    CASE WHEN CZCUR < AVG_WKLY_POS THEN AVG_WKLY_POS
    ELSE CZCUR END
    ELSE AVG_WKLY_POS END END AS REC_TTL
, CASE WHEN F.BASE_FCST > F.TTL_FCST THEN ((F.BASE_FCST*REC_TTL*1.00)/F.TTL_FCST)
 ELSE ((F.BASE_FCST*1.00)/NULLIFZERO(F.TTL_FCST))*REC_TTL END AS REC_MEAN
 , CASE WHEN BASE_FCST = 0
  THEN 0
  ELSE ((REC_MEAN - BASE_FCST)/BASE_FCST )*100.00 END AS PCT_DIFF

FROM WM_AD_HOC.NS_CK_SKU_FCST F
 , WM_AD_HOC.NS_SKU S
 , WM_AD_HOC.NS_ITEM_POS P
 , WM_AD_HOC.NS_ITEM I
 
WHERE F.STORE_NBR = S.STORE_NBR
 AND F.ITEM_NBR = S.ITEM_NBR
 AND F.ITEM_NBR = P.ITEM_NBR
 AND F.ITEM_NBR = I.ITEM_NBR
 AND F.TTL_FCST>0
 AND F.BASE_FCST >0
 AND F.TTL_FCST <> REC_TTL
-- AND ABS(REC_MEAN - TTL_FCST)>3