Diciamo che non lo sappiamo
I've just started this section so this might be a silly question. Diciamo che non lo sappiamo - "Let us say we do not know it". The notes that come with this "imperative" unit state that pronouns are often (can be ?) built into the appropriate verb. So, could this sentence also be " Diciamoci che non sappiamolo". ?
Only "diciamo" is in the imperative, so you can't stick the pronoun on the end of "sappiamo" (it's just a normal present tense verb). You could technically put "ci" onto "diciamo," but it changes the meaning from "let's say" to "let's tell ourselves/each other." Grammatically correct, but I don't know that I would accept it as a translation for "let's say."
You could have more than one, but they're typically main verbs in the sentence (so not often used in subordinate clauses), which means if there is more than one, they are tied together by words like "and," "or," etc. For example: "Andiamo a casa e dormiamo un po'!" ("Let's go home and [let's] sleep a little!").
It's a fine question. "Diciamoci che non sappiamolo" is wrong. "Diciamoci che non lo sappiamo" is correct. You can use "sappiamolo" (alone) or "allora sappiamolo!" only for "che noi lo si sappia" (it's could be "plurale maiestatico" or not). It's complicated, because these problems derive from the abandonment of the Latin declinations. (they was clearer !). Another translation, i.h.m.o., more literary, could be "lasciaci dire che noi non lo sappiamo". To let indicates an imperative, but also "lasciare". @mmseiple, I'm wrong ?