Hi,
I would like to organize my (huge) foto collection using tags. So i would like to know if there is a feature in zenphoto to create a taxonomy using tags and subtags like

Colors
----->Red
----->Green

Architechture
----->Medieval
---------->Early medieval
---------->High medieval
---------->Late medieval
----->Renaissance
---------->A
---------->B
---------->C
---------->D

etc etc.

Thanks in advance!

No and it is not planned either. Tags are by definition not nested anyway IMHO.

Try to use real albums or dynamic albums for that purpose.

I had originally wanted to do that too. I did what acrylian suggested - albums with dynamic albums standing in for subalbums. I placed the dynamic albums inside of real albums that don't contain any images.

I wanted:
Insects
--Bugs
----Assassin and Ambush Bugs (images contained in this folder)

I used:
Insects
-- Bugs (album - all images contained in this folder)
----View By Family (album - no images in this folder, only dynamic albums)

If you'd like to see how it works, it's at http://donnabrunet.com/images/stock/