The rapacity and venality of London councils never ceases to astonish, does it ?
Both PCNs have the same contravention of entering a pedestrian zone, and at the same time ! But you entered at one end, and exited at the other, so there was only one contravention. So for the PCN at the location where you left the zone, you should submit representations referring to the other PCN and point out that you only entered once, therefore the second PCN must be cancelled.
As to the first PCN, their photos would seem to show you driving past two clear "Flying Motorbike" signs head-on. Is this the case ? If so, then this will be difficult to overturn. Were you blindly following a satnav ? GSV is not up-to-date here, (March 2022), so doesn't show the signs, making it difficult to see if there is a problem with sign visibility. Any reason at all why you missed seeing them ? This is a 20 mph road as far as I know, so slow enough to see and read the times on the signs, I would have thought.
Probably the best approach is to submit reps against both PCNs in a single letter, pointing out the fact that there was only a single contravention, indeed the time on both PCNs is identical. Say that you consider two PCNs for a single offence is grossly disproportionate and also against common law that one can only be punished once for a single offence. State that you are prepared to pay the first PCN at the discounted rate.
Other than the above, there may be a technical appeal argument based on Newham mismanagement of the enforcement process. This is totally unrelated to the contravention, but has one appeals recently. The downside is that these are only considered at London Tribunals with the full PCN penalty in play. One of our contributors may come on here and suggest such an appeal.