Repeated Summation of group of numbers in large number of data

Hello
I want to get the summation for first 24 data, then next 24 data and so on as per the D column. I tried with =SUMIF(A2:A25, "<>0", C2:C25) equation. But it doesn't work. I know it is something similar to =IF(A2=0, AVERAGEIF(C2:C25, "<>0", C2:C25), "") format, which is used in E column to get the average value. But it is rather difficult to modify. Kindly help me. I hv attached the sheet.