In a manner that affects or relates to both sides equally; bilaterally in a truly symmetric way.
From ambilateral + -ly. This appears to be a constructed or theoretical form combining ambi-, lateral, and -ally, though it's not commonly attested in actual usage.
This might be the most awkwardly constructed word in your list—saying it out loud shows why English prefers shorter forms like 'bilaterally' rather than piling Latin roots together into tongue-twisters.
Complete word intelligence in one call. Free tier — 50 lookups/day.