"Montage zygomatique" should be most definitely "assembly," the way how the little zygots or whatevers are assembled in the body or wherever... :-) I'm more of a literary type than scientific... :-)

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&d...

If any of this is by any chance a device, than it should be "installation."

Mosby Med. Dict.

it may mean setup in this context; in other contexts it is assembly

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Note added at 17 mins (2005-10-05 22:41:32 GMT)
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Zygomatic
Main page for Zygomatic. ... The Zygomatic System. About Zygomatic ... You will need mtools and bochs to take advantage, but this works in both my Linux and Cygwin development setups. I do ...zygomatic.sourceforge.net - 9k - Cached - More from this site - Save - Block
Animal Jewelry
... Powerful - Stock Trading - Systems and Setups. Original ProgramsComputer monitoring, privacy, and security ... refers to the observable bend of the zygomatic arches in the skull ...bonose.com/Animal+Jewelry-52.html - 19k - Cached - More from this site - Save - Block

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Note added at 22 mins (2005-10-05 22:46:37 GMT)
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Doctors also refer to this as "process." It not only refers to location as Georges points out but also the setup (i.e., the actual electrode as assembly, if you will, so PROCESS may be more in line with the overall meaning.

Parkland Doctors ARRB
The Parkland Doctors ARRB Interview. 27th August 1998 9.13 am. Offices of University of Texas. Southwest Medical Center. 5323 Harry Hines Boulevard. PROCEEDINGS. RONALD COY , M.D. ROBERT M. McCLELLAND, M.D. MALCOLM O. ... I thought there was a wound on the left temporal area right in the hairline and right above the zygomatic process." ...www.paulseaton.com/jfk/parkland_arrb/park_arrb.htm - 110k - Cached - More from this site - Save - Block
watauga medical center operating room preceptor checklist ...
... Tibial osteotomy 29. Zygomatic fracture ENDOCRINE/LYMPHATIC SYSTEM PROCEDURES 1 ... MAGNET FRACTURE TABLE (STANDARD AND INTERMEDULLARY SETUPS HAND TABLES HEAD LIGHTS K-THERMIA UNIT ...home.earthlink.net/~kremmert/ororient.txt - 74k - Cached - More from this site - Save - Block
Putative Feed-Forward Control of Jaw-Closing Muscle Activity During Rhythmic Jaw Movements in the Anesthetized ...
... Fig. 1. Experimental setups for recording masticatory force, masseteric electromyograph (EMG), and jaw ... along the upper border of the zygomatic arch. The inferior alveolar nerve ...jn.physiology.org/cgi/content/full/86/6/2834 - More from this site - Save - Block

I don't do EEGs but I am very familar with EKGs, which are somewhat analogous.
"T" as George says refers to the temporal bone, overlying the temporal lobe of the brain. Several leads may be placed in different positions across the temporal bone, and these are labelled T-1, T-2 etc. The positions never overlap.
The zygomatic lead obviously refers to the zygoma, which is a ridge of bone running from the front of the ear to near the lateral eye, so I would judge this EEG position to be just anterior to the ear.
The zygomatic "process" is a process in the sense of a tissue outgrowth, not a procedure. ;-)

From your context, it seems that "montage" is referring to the electrode placement and/or lead, as George and Michael suggets - could also be referring to the tracing corresponding to the lead, but you don't give us enough context, so it's hard to say which word fits best.

I just wanted to point out that "montage" is used in English EEG language.

http://www.datex-ohmeda.com/clinical/cw_cong_article_TS.htm

Montage means the placement of the electrodes. The EEG can be monitored with either a bipolar montage or a referential one. Bipolar means that you have two electrodes per one channel, so you have a reference electrode for each channel. The referential montage means that you have a common reference electrode for all the channels.

http://apt.allenpress.com/aptonline/?request=get-abstract&is...

A digital EEG system allows the montage and filter settings to be determined at the time the EEG is reviewed, rather than at the time it is recorded. The EEG is recorded with minimally restrictive analog filter settings and with potentials at all electrodes measured with respect to a single common reference. A computer can then process the data as they are displayed on a screen or printer, reformatting the original referential montage to any desired referential or bipolar montage and digitally filtering the data as needed. If necessary, the same segment of EEG can be displayed repeatedly, using different montages and filters. This results in a significant advantage of digital EEG systems over analog, with better ability to distinguish normal from abnormal and epileptiform from nonepileptiform patterns. The Laplacian montage and spatial filtering of EEG using principal component analysis are other potentially useful digital techniques, which may aid the interpretation of EEGs.