Exegesis:

kai etarachthē Zacharias idōn lit. ‘and Zechariah having seen, was perplexed.’ idōn in the aorist tense refers to an act preceding the event of the main verb; its object auton ‘him’ is to be understood from the preceding verse. Strictly speaking idōn, as a conjunctive participle, goes syntactically with etarachthē only, and not with the subsequent clause but semantically that clause kai phobos epepesen ep’ auton ‘and fear fell upon him’ is as much determined by the fact that Zechariah saw the angel, as is etarachthē (cf. Phillips, An American Translation, Willibrord).

tarassō (also 24.38), in the passive ‘to be startled,’ at the sight of something supernatural.

kai phobos epepesen ep’ auton ‘and fear fell upon him,’ see above.

phobos ‘fear,’ ‘sense of awe,’ in Luke always of the reaction upon some supernatural happening as the appearance of an angel (1.12; 2.9), a miraculous healing (5.26), a raising from the dead (7.16) or some terrifying experience (8.37; 21.26). Because it is here parallel to etarachthē the emphasis is rather on ‘fear’ then on ‘a sense of awe.’

epipiptō (also 15.20) ‘to fall upon,’ ‘to take hold of,’ here with phobos as in Acts 19.17.

Translation:

The translator should ascertain what is the normal way to express transition in the receptor language, and translate accordingly. Such a procedure leads in some cases (e.g. in Malay) to the use of a transitional word, roughly to be rendered ‘then,’ or ‘next,’ with approximately the same frequency and regularity as in the Greek; elsewhere to the omission of such a word (as is often done in modern western versions), or, to its being replaced by a transitional construction, such as a special word, phrase, or clause order; or again to the insertion of a transitional phrase summarizing part of what precedes. In some cases it is better to change from co-ordination to subordination, subordinating the ‘and’-clause to what precedes, or the reverse. Finally, it is often necessary to use connectives that state the relationship between the sentences or clauses more explicitly than does the original, e.g. ‘afterward’ (2.20), ‘meanwhile’ (1.21a), ‘consequently’ (1.63b), ‘at-that-moment’ (4.17)

Was troubled, see below on “greatly troubled” in v. 29.

And fear fell upon him, or, ‘fear gripped him’ (Tamil, Kannada, Kituba); or, avoiding the shift of subject, from Zechariah to fear, “he was … overcome with fear” (An American Translation, similarly in Javanese). Expressions referring to fear occur rather often in this Gospel. The simplest and most frequent form is ‘to fear,’ or, ‘to be afraid’ (e.g. 8.50; 12.4f; 22.2; or, 1.13; 8.25; 9.34); other phrases are used to bring out the ingressive aspect, cf. “fear came on all” (1.65), “fear seized them” (7.16), “they were frightened” (24.5), or a certain degree of suddenness (here) and intensity, cf. “they were filled with fear” (lit. ‘they feared with a great fear,’ in 2.9), “they were filled with awe” (5.26), “they were seized with great fear” (8.37). Further occurrences of “fear” or “afraid”: 1.13, 30, 65, 74; 2.10; 5.10; 8.35; 9.45; 12.7, 32; 19.21; 20.19; 21.26; 22.2. For “to fear God” see on 1.50. The concept ‘to fear’ is sometimes to be rendered by idiomatic expressions such as, ‘the heart trembles’ (Tzeltal), ‘to feel him creep’ (Ngäbere), ‘to shiver in the liver’ (Uduk), ‘to have a little heart’ (Tzotzil), ‘to have a light heart’ (Kabba Laka, contrasting with ‘a hard heart’ for ‘courage’); or, more strongly emotive, ‘their thoughts left them,’ ‘their hearts fell.’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.