The highest "real" speed I've gotten with either TMZ or Delta 3200 is EI 1250, both in Microphen (straight). That's "real" based on the usual .10 DU above fb&f for a zone I exposure, meter calibrated to "sunny f16" and exposed using a Wallace Expo-Disc and developed to a "normal" contrast as I would also develop HP5+, Delta 100 etc. If you subscribe to the probably-valid assertion that it should be 12%-13% rather than 18% reflectance (or transmission), that would put both films at about EI 1000.(posted 8780 days ago)At any rate, no matter what elevated EI and lengthened development you give them, that's all the shadow density there is.
With extended development the toe area does _not_ rise in density any significant amount.
The biggest difference between TMZ and Delta 3200 is in curve shape; TMZ has a rather straight-line response similar to HP5+ while Delta 3200 has a very significant shoulder. The curve shapes don't change with different developers.
Depending on the subject contrast, printing methods etc, TMZ could be considered to have dense, virtually unprintable highlights _or_ good highlight contrast, while Delta 3200 may have easily-printable highlights _or_ muddy low highlight contrast.
For me the "sweet spot" is Delta 3200 at EI 1600-2000 developed in Microphen 7'/75F or DD-X 1:4 11'/75F.
If you don't want to mix powder, DD-X is a liquid concentrate that behaves like Microphen although development times are normally somewhat longer.
Also, if you experiment with Delta 3200, some of Ilford's exposure and development recommendations appear to have no connection to reality.