I've written the next sentence
If you explained what you are trying to achieve, I would recommend a kind of workaround.
and it has raised doubts about the tense I should have used in the highlighted phrase.
The options I see:
Which one is correct? Can both of them be used?
Thank you in advance.
The sentence below is an example of using the past subjunctive in English; therefore, no tense is being used and, thus, verbs don't always have to correlate:
If you explained what you are trying to achieve, I would recommend a kind of workaround.
The verb "to explain" has equivalent forms in the past indicative as it does in the past subjunctive:
to explain (all forms in both paradigms are "explained")
I explained: first-person singular past indicative
I explained: first-person singular past subjunctive
In fact, the only verb in Modern English that shows a difference in its past subjunctive form when compared to its past indicative form is "to be":
to be
I was: first-person singular past indicative
I were: first-person singular past subjunctive
If you were to use "thou" or read "thou" in old literature, it would have a different form in the past subjunctive when compared to its past indicative form; however, the rule isn't always followed in old literature like Shakespeare and the King James Bible because "thou" was on its way out when the rules of grammar were being written; however, in Old and Middle English, it was followed (circa A.D. 600 to circa 1400):
to sit
thou sattest: second-person singular past indicative
thou sat: second-person singular past subjunctive
So here are some Modern English constructions using the archaic "thou" and its paradigm:
"Thou sattest at thy desk yesterday." (present indicative)
"Thou wouldst always play with dolls when thou wast / wert young." (past indicative)
"If thou sat at thy desk now, thou would get thy work done." (past subjunctive)
I would like to reiterate that the paradigm using "thou" above is not always consistent in Early Modern English because English grammar had not been formalized until about A.D. 1650, so these forms are not always consistent in literature. Despite the inconsistencies, if "thou" had survived into Modern English, this would have been most likely the prescribed paradigm.
Now getting back to your initial question: because the first verb of the protasis ("if" part of "if-then" statement, i.e. "explained") must be in the past subjunctive mood as well as the first verb of the apodosis ("then" part, i.e. "would"), this doesn't mean that the verbs of subordinate clauses have to be in the past subjunctive. There are times when conjunctions are used such as "before", "until", or "if", etc. wherein the past subjunctive would have to be used or technically should be used, but, in this instance, that is not the case:
If I explained it until I were blue in the face, you wouldn't understand what I am talking about.
This rule, however, is not always followed in Modern English. Many native speakers don't use the past subjunctive form with conjunctions like "before" and "until" anymore because they don't use them in their present subjunctive forms anymore particularly with conjunctions such as "before" and "until"; however, I am giving you the "proper" English construction and not necessarily the way it is often said.
P.S. Perhaps I didn't make it clear enough when I said above that the original example can mean the exact same thing whether it be "you are trying to achieve" or "you were trying to achieve". It is often said the way in the examples below and many native speakers hearken to this way of saying it:
"If I knew that he was cheating (now), I would tell you what was going on."
"If I were the person who was in charge (now), I would do it this way so that no one would be the wiser."
In the first example, "knew" in the protasis and "would" in the apodosis are in the past subjunctive whereas "was" in the protasis and "was" in the apodosis, both of which are emboldened in print just as I have emboldened their equivalents in the second example, are in the simple past tense. This is how many native speakers say it now because they try to align the verbs in subordinate clauses so that they look like their past subjunctive counterparts in the main clauses, and each example above does mean the same thing as it would if the verbs in the subordinate clauses were in the present tense, i.e., in the second example, "is" and "will" instead of "was" and the second "would".
In essence, what I am trying to say is that it could be said this way as Andrew has stated in his comment to your question above:
"If I knew that he is cheating (now), I would tell you what is going on."
"If I were the person who is in charge (now), I would do it this way so that no one will be the wiser."
This second way is less common and it clearly shows the subjunctive verbs. It is a matter of style in English now. Do you want to clearly point out that the information in the subordinate clauses are happening in the present tense or do you want it to appear to align in form with the past subjunctive verbs of the main clauses? That is often up to the writer or speaker who is using these constructions. The subjunctive is a tough subject in English because it looks so much like the past and present tenses in Modern English. Because of this, the rules are all over the place. I would tell you that you could use both "you are trying" and "you were trying" in your original example and you would have the same meaning because this is a rule that is not consistent in Modern English. I wish it were an easier subject to explain.
I hope this might have helped you out. Take care and good luck.
