Try the outline of this one first, then add the details. The D-E-D needs to be neatly fingered every time, have a good full tone (no ghosty notes), yet also be the accompaniment part.
Tongueing is often used to cover up poor aim. Each of those T’s can be used to kick each note into life, but this doesn’t make a good experience for the listener (who only wants to hear expressive music).
Diaphragm work first and foremost. We want to hear beautiful bell-like tones rather than a series of T’s. So, try it without tonguing first. You may well need a quick session on the Pneumo-Pro to remind you about what should be happening in middle octave tone production.
A bit of both. Flowed notes bursting into separates (I dread to use the word ‘staccato’ as it seems to invoke a bar of T’s rather than tones). Diaphragm energy used for both styles: the legato bars need to surge forward rather than just be joined notes. It might only be four bars, but let’s make music that turns people’s heads.