The zarka and segolta on מַעֲשֵׂה חָרַשׁ אֶבֶן

Summary: Shadal writes that one would expect it to be different, based on Rashi. One should put חָרַשׁ אֶבֶן together as a single phrase.

Post: Consider the following pasuk and Rashi towards the start of parashat Tetzaveh:

11. [Similar to] the work of an engraver of gems, [similar to] the engravings of a seal, you shall engrave the two stones with the names of the sons of Israel; you shall make them enclosed in gold settings.		יא. מַעֲשֵׂה חָרַשׁ אֶבֶן פִּתּוּחֵי חֹתָם תְּפַתַּח אֶת שְׁתֵּי הָאֲבָנִים עַל שְׁמֹת בְּנֵי יִשְׂרָאֵל מֻסַבֹּת מִשְׁבְּצוֹת זָהָב תַּעֲשֶׂה אֹתָם:
[Similar to] the work of an engraver of gems: Heb. אֶבֶן מַעִשֵׂה חָרַשׁ. The work of a craftsman of precious stones. This [word] חָרַשׁ is connected to the following word. Therefore, it is vowelized with a “pattach” at the end, and likewise, “The carpenter (חָרַשׁ עֵצִים) stretched out a line” (Isa. 44:13). [This is like] חָרָשׁ שֶׁל עֵצִים. Likewise, “The iron smith (חָרַשׁ בַּרְזֶל)” (Isa. 44:12). All these are connected and are [therefore] vowelized with “pattach” s.		מעשה חרש אבן: מעשה אומן של אבנים. חרש זה דבוק הוא לתיבה שלאחריו, ולפיכך הוא נקוד פתח בסופו, וכן (ישעיה מד יג) חרש עצים נטה קו, חרש של עצים. וכן (ישעיה מד יב) חרש ברזל מעצד, כל אלה דבוקים ופתוחים:
[similar to] the engravings of a seal: Heb. פִּךְתּוּחֵי חֹתָם, as the Targum [Onkelos] renders: כְּתַב מְפָרָשׁ כִּגְלָף דְּעִיזְקָא [a clear script like the engraving of a signet]. The letters are engraved inwardly, as they engrave the seals of signets, which are [used] to seal letters, [in] a clear and explanatory script.		פתוחי חותם: כתרגומו כתב מפרש כגלף דעזקא, חרוצות האותיות בתוכן, כמו שחורצין חותמי טבעות שהם לחתום אגרות, כתב ניכר ומפורש:

The trup on the pasuk is:

which means that maaseh charash is placed together, and separated from the word even. This is strange, because according to Rashi's parse, the charash even should stand together, and it is the maaseh | of the charash even.

The alternative parse would seem to be that it would be the maaseh of a charash, upon even. Would be expect that nikkud, though?

Anyway, this is just what Shadal observes. He writes: 

That is, the zarka is disjunctive trup dividing a clause which ends with the segolta. So we should have expected the zarka dividing mark on the word maaseh, to keep charash even together. Perhaps the alternative parse is: engraver's work, upon gems.