When reading the megilloth in shul from a klaf, many say the blessing of shehechiyyanu1. I have noticed that many people sing this blessing in its own tune (ie. not in trope), but I have also heard it read using the trope about to be used for that megillah.
In order to use trope, we need to first grammatically parse the sentence.
For the parsing of the first half, see this question2. For the second half, do we understand:
(a) (שהחינו וקימנו והיגענו) (לזמן הזה)
where לזמן הזה applies to all the verbs3, or
(b) (שהחינו וקימנו) (והגיענו לזמן הזה)
where לזמן הזה only applies to the last verb4?
1 See S"A O"H 692:1 for Esther, Ma'aseh Rav 175 for Shir HaShirim. See also sources here and here.
2 Perhaps one would do: pashta munach zakef-qaton tipcha munach etnachta.
3 Hence, perhaps: darga tvir tipcha mercha siluq (cf. Deut 33:27).
4 Hence, perhaps: pashta zakef-qaton tipcha mercha siluq (cf. Num 4:31). I would think something similar also applies to the blessing על מקרא מגילה: mapakh pashta zakef-qaton tipcha mercha siluq (cf. Ex 33:10) (or arguably pashta munach zakef-qaton).