Improving performance of zreport

Hi,

I have on requirement of improving performance of zreport.

(1) Apart from nested loops, select within loop, inner joins, is there any other changes i have to consider.

(2) There 4 nested loops found, which have upto 1 level. Is it mandatory for avoiding nested loops which have upto 1 level?

(3) How to avoid SELECT, ENDSELECT within LOOP and ENDLOOP

(4) The FM WS_DOWNLOAD, which is outdated is called for downloading data into excel. Which one i have to choose for replacing this FM.

I will reward, if it is useful.