merge with case

I need your help pls...I have a requirement in merge -

how do I handle below scenario? I know i can't put 3 matched. 

when matched and s.efforts =0 then update table1 set field1=somevalue, field2=somevalue

when matched and s.efforts <>0 and target.field1<>0 then update table1 set field1=source.somevalue, field2=target.somevalue

when matched and s.efforts <>0 and target.field1=0 then update table1 set field1=source.somevalue, field2=target.somevalue