Vlookup with conditions

I would like to create a formula that performs a vlookup using ISNA to return zero for those conditions and then apply a conditional calculation to that returned answer but am having difficulty constructing it. I'm fine with the vlookup function, but then when I get that answer I'm not sure how to apply the remaining conditions. For example, if there is an amount in column D, then I'd like to divide that by 12 and spread to months. Likewise if there is an amount in column E, I'd like to take the previous vlookup answer and multiply it by this cell. Any suggestions on the best way to do this?

Thanks much for any assistance!
Mark