To sum up –
if there is an "is" after "this" – safely remove it, and this is it
If there is no "is" – then "this" works like an adjective! Then the words change places (and "this" goes after the word it describes)
Consider this chain:
"This is a book" – זֶה סָפַר
Then, "this is an interesting book" – זֶה סֵפֶר מְעַנְיֵן
"The interesting book is on the shelf" – הַסֵּפֶר הַמְּעַנְיֵן עַל הַמַּדָּף.
"This interesting book is on the shelf" – הַסֵּפֶר הַמְּעַנְיֵן הָזָה עַל הַמַּדָּף.
"This book is on the shelf" – הַסֵּפֶר הָזָה עַל הַמַּדָּף
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That's it, זַהוּ זֶה!
I hope it's all clear now! If not completely – you know what to do!
Write to me, ask me, - I am here to help you understand and speak Hebrew. ????
Happy Hebrew-learning,
Alisa