Combination Soul absorbing bone tower + Zombie world

So I have this combination in my deck and my question is: If I have zombie world active on the field, making all monsters on the field and graveyards into zombie type monsters

And I have soul absorbing bone tower, that when a zombie type monster is special summoned I destroy two cards from the top of my opponent's deck.

If he special summons a, let's say spell caster, monster, does it count as a zombie special summon?

Yes, yes it does.

Because all monsters on the field are zombie monster are on the field and thus when the you opponet special summons a non-zombie monster while Zworld is on the field it is treated as a zombie when special summoned.

Also why you can't tribute a monster to summon caius while Zworld is on the field :/

all right thanks, I thought that it wouldn't work since untill the monster is on the field it would be treated as it normally is, spellcaster, warrior etc. Thanks for the help

the rationale:

Bone Tower's effect activates whenever a Zombie is successfully special summoned. When summoning a monster, you 1st attempt to summon, at which point the summon can be negated (i.e. Solemn Judgment/Warning ...etc). The monster is not yet on the field at this point. If the summon is successful, however, the monster is now on the field, and since it is at this time that Bone Tower activates, the monster is a Zombie no matter what thanks to Zombie World since it is on the field.