Zero has definitely trademarked their name. The Goods and Services covered by "Zero Motorcycles" are:
Electric vehicles, namely, motorcycles; Motorcycles. FIRST USE: 20070629. FIRST USE IN COMMERCE: 20070629
Zero also holds the following trademarks:
Serial Number Reg. Number Word Mark Check Status Live/Dead
1 85189661 ZERO URBANCROSS TARR LIVE
2 85157817 ZEROCROSS TARR LIVE
3 77977387 3661976 ZERO TARR LIVE
4 77793886 ZERO DS TARR LIVE
5 77757810 ZERO MX TARR LIVE
6 77665631 3669261 Z-FORCE TARR LIVE
7 77665629 ZERO S TARR LIVE
8 77665628 ZERO SS TARR LIVE
9 77616233 ZERO X TARR LIVE
10 77960452 DISCOVER THE EXPERIENCE TARR DEAD
11 77377959 ZENERGY TARR LIVE
12 77160341 ZERO TARR DEAD
13 77191336 3669900 ZERO MOTORCYCLES TARR LIVE
For more info, go to
http://tess2.uspto.gov/bin/gate.exe?f=tess&state=4007:9qj98k.1.1and search for Zero Motorcycles under the "owner name and address" field. Unfortunately, they don't seem to allow linking directly to the search results or I'd provide that.
Yes, the have a trademark on Zero X. It is listed as:
: Electric motorcycles; Motorcycles and structural parts therefor; Motorcycles for motocross
Could they advance a claim of trademark infringement against Honda? Sure. Would they win such a claim? Who knows?