There is a similarity and difference between the prophets/messengers. The similarity is that they are all equal in being appointed as divine messengers and authorities. The difference is with respect to the nature of their position with Allah, and their own circumstances.
So, these two verses reflect those two things.
2:136 is a statement of belief for us to profess. That is, WE must accept all the prophets/messengers as being equal in their validity. We must accept them all as having correct messages from Allah that are consistent with the messages of the other prophets. We are not allowed to accept some and reject others. This verse is in the context of criticizing the Jews and Christians for accepting some and rejecting others.
However, this does not mean that all the prophets and messengers were identical, as indicated in 2:253 and elsewhere. The prophets and messengers each had their unique circumstances and positions with Allah. For instance, Jesus was born in a unique way, Solomon had a unique kingdom, and the Prophet Muhammad (S) is considered to be the highest of the messengers.