Is it preferable to pause between the two "takbirs" of the Adhan, or is it obligatory to connect them, or is there flexibility in the matter?

All phrases of the Adhan (call to prayer) must have their last letter in the jazm (jussive) case. There is a difference of opinion regarding the first two takbirs (utterances of "Allahu Akbar"): should their last letter be in the jazm case or not? This is the operative view within the Maliki school, where there is a difference of opinion, and both are permissible. This difference of opinion is specific to the first two takbirs. As for the other words of the Adhan, their jazm is among their essential characteristics. Therefore, there is no obligation to connect or pause between the first two takbirs.