Difference between Apple's Thunderbolt ethernet adapters?
I think there are no differences in the hardware, just the regional identifier for the product. There might be differences in the packaging however. Here in Eastern Europe the ZM model is being sold.

Here is an incomplete list of country codes (unconfirmed, source):


AB - Egypt, Saudi Arabia, United Arab Emirates
B - Ireland, UK, also used for some replacement phones
C - Canada
CZ - Czech Republic
DN - Austria, Germany, Netherlands
E - Mexico
EE - Estonia
ER - Ireland
FB - France, Luxembourg
FD - Austria, Liechtenstein, Switzerland
GR - Greece
HN - India
IP - Italy
J - Japan
KH - Korea
KN - Norway
KS - Finland, Sweden
LA - Colombia, Ecuador, El Salvador, Guatemala, Honduras, Peru
LE - Argentina
LL - USA
LZ - Chile, Paraguay, Uruguay
MG - Hungary
MY - Malaysia
NF - Belgium, France, Luxembourg
PL - Poland
PO - Portugal
PP - Philippines
RO - Romania
RS - Russia
SL - Slovakia
SO - South Africa
T - Italy
TA - Taiwan
TU - Turkey
X - Australia, New Zealand
Y - Spain
ZA - Singapore
ZP - Hong Kong, Macau, Malaysia


Here is another article showing explaining Apple product codes.