Welcome to the forum.
"0" is text, change it to just 0
=IF(B13<B11*0.70, B13=0),IF(B13=(B11>=0.7,B11<0.99, B13*0.075)))
Also, your formula stops at the 1st if. what exactly are you trying to do?
OK try this
=B13*LOOKUP(B13/B11,{0,0.7,1,1.21},{0,0.075,0.1,0.125})