Exegesis:

legontes ‘saying,’ here referring to an act distinct from the verb with which it goes, i.e. apēgagon.

ei su ei ho Christos, eipon hēmin ‘if you are the Messiah, tell us (so).’ ei is conditional, not interrogative ‘whether.’

ean humin eipō ou mē pisteusēte ‘if I tell you (i.e. that I am the Messiah), you will not believe me.’ For ou mē cf. on 1.15.

(V. 68) ean de erōtēsō ‘if I ask you,’ either in a general sense (cf. New English Bible) and referring to situations like e.g. 20.41, or specifically, ‘whether you think I am the Messiah,’ preferably the former.

ou mē apokrithēte ‘you will not answer,’ cf. on 1.15. Like ou mē pisteusēte in v. 67 the clause expresses strong conviction on the part of Jesus.

Translation:

If you are. In languages like Thai and Javanese the high priest, by not using honorifics, shows his conviction that Jesus cannot be the Christ. The same holds true for v. 70.

For believe, i.e. ‘believe me (or, it, or, my words),’ cf. on 1.20.

(V. 68) Ask you, or, ‘ask (you) questions,’ ‘ask you something’ (Tae’ 1933).

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.