The structure 纵然…也… forms subordinate complex sentences and indicates that some result happened despite circumstances that may make the result seem unlikely.
For example: “even though he did wrong, we still remain friends”.
In the first part, after 纵然, we state a possible or existing circumstance. In the second part, after 也, we state the result that won't change despite the stated circumstance.
We can state the subject either before 纵然 or before 也.
Even if a long time passes, I will never forget you
zòngrán shíjiān xiāoshì, wǒ yě bú huì wàngjì nǐ
Even though their ideas are not the same, they have to support each other
tāmen de xiǎngfǎ zòngrán bù yíyàng, yě yào hùxiāng zhīchí
Even if his behavior is not good, it is still their problem. It doesn’t concern us
tā de xíngwéi zòngrán bù hǎo, yěshì tāmen zhī jiān de shì, wǒmen bú yào guǎn le
Usually there is a negation in one part of the sentence.
Sometimes 纵然 can be replaced by 纵使 in the structure.
Even if it rains tomorrow, they are going on the excursion
zòngshǐ míngtiān xià yǔ, tāmen yě yào qù yóulǎn
Even if the result is not zero today, it will still be zero in the future
zòngshǐ jīntiān de jiéguǒ bú shì líng, jiānglái yě huì shì líng de