Having trouble putting a formula together.

I have the following formula which works:

Scenario : $d$d = either Weight or Unit or Unknown (of an ingredient)
e8= is a quantity number ( either in grams or units, of an
ingredient. eg 100 or 1)
Raw data is in Nutrition!$b$6:$g$70

The following formula works so far:

f8 ( which is the no. of calories)=if($d$d="weight",e8/100,e8)*vlookup(c8,
Nutrition!$b$6:$g$70,3,false)

But I also want to add to it that

If e8(quantity)=0 or blank or invalid then "qty?" should appear in the f8
cell

The following formula works:
f8=if(or(e8=0,istext(e8)),"qty?",vlookup(c8,Nutrit ion!$b$6:$g$70,3,false))

But I cant seem to combine the two statements to so that

Am completely stuck here, need help asap.

lozzam