Is there a reduction when you say "is there "or "is this"?
I feel like native english speakers drop the voiced th sound in fast speech when they say "is there.... ?" and "is this...?". Can you tell me if I'm right or wrong . Thanks for your attention. I’m looking forward to your reply.
Six of one half dozen of the other: in other words, you're right but you're also wrong.
Not everyone assimilates these sounds. I don't personally, but have heard many people assimilate the two sounds: /ɪz ðɪs/ becomes /ɪz zɪs/ or /ɪ zɪs/.