* spot/twaalgos/zlktree.hh, spot/twaalgos/zlktree.cc (zielonka_tree_transform): New function. * tests/python/_zlktree.ipynb: Test it on three examples.
* spot/twaalgos/zlktree.cc, spot/twaalgos/zlktree.hh: New files. * spot/twaalgos/Makefile.am: Add them. * tests/python/_zlktree.ipynb: New file. * tests/Makefile.am: Add it. * python/spot/__init__.py, python/spot/impl.i: Add bindings for it. * doc/spot.bib (casares.21.icalp): New entry. * NEWS: Mention this.