Are your enemies destroyed in any other event where lives are not <=0 or Type is not <=1? If not then it doesn't matter that the "on destroyed" event isn't nested and the other conditions aren't needed.
If you have more than one type of enemy, or enemies are also destroyed in other events where their live value is greater than one then I'd use something like this:
Type <=1: Do A
Type =2: Do B
Type <=1: Do C
Type =2: Do D
The "On Destroyed" condition would be a top level event. Exactly how you order the rest of the hierarchy is dependent upon the conditions you have set up for destroying the different enemies: you may want to switch it instead to have the Lives conditions nested under the Type conditions.
What you definitely don't need is the "trigger once" condition with the "On Destroyed" condition, as "On Destroyed" will only trigger once per enemy that is destroyed anyhow.